v1.16: removes feature-gate code for updating rewards from cached accounts (backport of #32514)

[mergify]

This is an automatic backport of pull request #32514 done by Mergify.
Cherry-pick of 952d886 has failed:

On branch mergify/bp/v1.16/pr-32514
Your branch is up to date with 'origin/v1.16'.

You are currently cherry-picking commit 952d8861c6.
  (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:   runtime/src/accounts_db.rs
	modified:   runtime/src/bank/metrics.rs
	modified:   runtime/src/bank/tests.rs
	modified:   runtime/src/stake_account.rs
	modified:   runtime/src/stakes.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   runtime/src/bank.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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[codecov]

Codecov Report

Merging #32669 (605d1c3) into v1.16 (4b06538) will decrease coverage by 0.1%.
The diff coverage is 100.0%.

@@            Coverage Diff            @@
##            v1.16   #32669     +/-   ##
=========================================
- Coverage    82.0%    81.9%   -0.1%     
=========================================
  Files         762      762             
  Lines      207777   207634    -143     
=========================================
- Hits       170402   170214    -188     
- Misses      37375    37420     +45     

[behzadnouri]

Backporting this in order to backport #32633.

[jeffwashington]

lgtm. I think @willhickey needs to approve?

[behzadnouri]

This got merged automatically because of the automerge label.
@willhickey please confirm that you are ok with this or we can revert if not.