stake: Allow stakes with unmatched credits observed to merge (backport #18985)

[mergify]

This is an automatic backport of pull request #18985 done by Mergify.
Cherry-pick of 2b33c0c has failed:

On branch mergify/bp/v1.7/pr-18985
Your branch is up to date with 'origin/v1.7'.

You are currently cherry-picking commit 2b33c0c16.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   programs/stake/src/stake_state.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   Cargo.lock
	both modified:   programs/stake/Cargo.toml
	both modified:   sdk/src/feature_set.rs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[mergify]

automerge label removed due to a CI failure

[mergify]

automerge label removed due to a CI failure

[mergify]

automerge label removed due to a CI failure

[codecov]

Codecov Report

Merging #19055 (4901088) into v1.7 (7d0a9e0) will increase coverage by 0.0%.
The diff coverage is 99.0%.

@@           Coverage Diff            @@
##             v1.7   #19055    +/-   ##
========================================
  Coverage    82.3%    82.3%            
========================================
  Files         436      436            
  Lines      123179   123287   +108     
========================================
+ Hits       101390   101498   +108     
  Misses      21789    21789