deps: update module github.com/prometheus/client_golang to v1.21.1 (#878

)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
|
[github.com/prometheus/client_golang](https://redirect.github.com/prometheus/client_golang)
| `v1.21.0` -> `v1.21.1` |
[![age](https://developer.mend.io/api/mc/badges/age/go/github.com%2fprometheus%2fclient_golang/v1.21.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/go/github.com%2fprometheus%2fclient_golang/v1.21.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/go/github.com%2fprometheus%2fclient_golang/v1.21.0/v1.21.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/go/github.com%2fprometheus%2fclient_golang/v1.21.0/v1.21.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>prometheus/client_golang
(github.com/prometheus/client_golang)</summary>

###
[`v1.21.1`](https://redirect.github.com/prometheus/client_golang/releases/tag/v1.21.1):
/ 2025-03-04

[Compare
Source](https://redirect.github.com/prometheus/client_golang/compare/v1.21.0...v1.21.1)

This release addresses a major performance regression introduced in
[#&#8203;1661](https://redirect.github.com/prometheus/client_golang/issues/1661)
-- thanks to all who [reported this
quickly](https://redirect.github.com/prometheus/client_golang/issues/1748):
[@&#8203;chlunde](https://redirect.github.com/chlunde),
[@&#8203;dethi](https://redirect.github.com/dethi),
[@&#8203;aaronbee](https://redirect.github.com/aaronbee)
[@&#8203;tsuna](https://redirect.github.com/tsuna) 💪🏽. This patch
release also fixes the iOS build.

We will be hardening the release process even further
([#&#8203;1759](https://redirect.github.com/prometheus/client_golang/issues/1759),
[#&#8203;1761](https://redirect.github.com/prometheus/client_golang/issues/1761))
to prevent this in future, sorry for the inconvenience!

The high concurrency optimization is planned to be eventually
reintroduced, however in a much safer manner, potentially in a separate
API.

- \[BUGFIX] prometheus: Revert of `Inc`, `Add` and `Observe` cumulative
metric CAS optimizations
([#&#8203;1661](https://redirect.github.com/prometheus/client_golang/issues/1661)),
causing regressions on low concurrency cases
[#&#8203;1757](https://redirect.github.com/prometheus/client_golang/issues/1757)
- \[BUGFIX] prometheus: Fix GOOS=ios build, broken due to
process_collector_\* wrong build tags.
[#&#8203;1758](https://redirect.github.com/prometheus/client_golang/issues/1758)

<details>
<summary>All commits</summary>

- Revert "exponential backoff for CAS operations on floats" and cut
1.21.1 by [@&#8203;bwplotka](https://redirect.github.com/bwplotka) in
[https://github.com/prometheus/client_golang/pull/1757](https://redirect.github.com/prometheus/client_golang/pull/1757)
- Fix ios build for 1.21.1 by
[@&#8203;bwplotka](https://redirect.github.com/bwplotka) in
[https://github.com/prometheus/client_golang/pull/1758](https://redirect.github.com/prometheus/client_golang/pull/1758)

</details>

**Full Changelog**:
prometheus/client_golang@v1.21.0...v1.21.1

</details>

---

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---

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---

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View the [repository job
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go.mod

@@ -6,7 +6,7 @@ toolchain go1.23.6
 
 require (
 	github.com/hetznercloud/hcloud-go/v2 v2.19.1
-	github.com/prometheus/client_golang v1.21.0
+	github.com/prometheus/client_golang v1.21.1
 	github.com/spf13/pflag v1.0.6
 	github.com/stretchr/testify v1.10.0
 	github.com/syself/hrobot-go v0.2.6

go.sum

@@ -158,6 +158,8 @@ github.com/prometheus/client_golang v1.20.5 h1:cxppBPuYhUnsO6yo/aoRol4L7q7UFfdm+
 github.com/prometheus/client_golang v1.20.5/go.mod h1:PIEt8X02hGcP8JWbeHyeZ53Y/jReSnHgO035n//V5WE=
 github.com/prometheus/client_golang v1.21.0 h1:DIsaGmiaBkSangBgMtWdNfxbMNdku5IK6iNhrEqWvdA=
 github.com/prometheus/client_golang v1.21.0/go.mod h1:U9NM32ykUErtVBxdvD3zfi+EuFkkaBvMb09mIfe0Zgg=
+github.com/prometheus/client_golang v1.21.1 h1:DOvXXTqVzvkIewV/CDPFdejpMCGeMcbGCQ8YOmu+Ibk=
+github.com/prometheus/client_golang v1.21.1/go.mod h1:U9NM32ykUErtVBxdvD3zfi+EuFkkaBvMb09mIfe0Zgg=
 github.com/prometheus/client_model v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
 github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
 github.com/prometheus/common v0.55.0 h1:KEi6DK7lXW/m7Ig5i47x0vRzuBsHuvJdi5ee6Y3G1dc=