fix do_set_weights to use commit_block in commit reveal

[andreea-popescu-reef]

Description

Currently, do_set_weights sets last updated block to the current (reveal) block - this should be set to the weights commit block.
If not fixed, for concealment period > 1 tempo, the current implementation will unjustly distribute incentive whenever an uid re-registers between the commit and reveal block

Related Issue(s)

N/A

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[olzhasar-reef]

Not related to your changes,
I'm not sure why is this being converted to reference if it's still being dereferenced everywhere below, but I don't have any experience with Rust, maybe it's how it works:

            let (commit_hash, commit_block) = maybe_commit
                .as_ref()
                .ok_or(Error::<T>::NoWeightsCommitFound)?;