Bump kotestVersion from 5.8.0 to 5.9.1

Bumps `kotestVersion` from 5.8.0 to 5.9.1.

Updates `io.kotest:kotest-assertions-core` from 5.8.0 to 5.9.1
- [Release notes](https://github.com/kotest/kotest/releases)
- [Commits](kotest/kotest@v5.8.0...v5.9.1)

Updates `io.kotest:kotest-assertions-json` from 5.8.0 to 5.9.1
- [Release notes](https://github.com/kotest/kotest/releases)
- [Commits](kotest/kotest@v5.8.0...v5.9.1)

Updates `io.kotest:kotest-extensions` from 5.8.0 to 5.9.1
- [Release notes](https://github.com/kotest/kotest/releases)
- [Commits](kotest/kotest@v5.8.0...v5.9.1)

---
updated-dependencies:
- dependency-name: io.kotest:kotest-assertions-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.kotest:kotest-assertions-json
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.kotest:kotest-extensions
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

build.gradle.kts

@@ -1,6 +1,6 @@
 val javaVersion = JavaVersion.VERSION_21
 val ktorVersion = "2.3.12"
-val kotestVersion = "5.8.0"
+val kotestVersion = "5.9.1"
 val jacksonVersion = "2.16.0"
 val mockkVersion = "1.13.8"
 val felleslibVersion = "0.0.129"