Cleanup serde snapshot's "future" to "newer" (backport #22431)

[mergify]

This is an automatic backport of pull request #22431 done by Mergify.
Cherry-pick of 9c3144e has failed:

On branch mergify/bp/v1.9/pr-22431
Your branch is up to date with 'origin/v1.9'.

You are currently cherry-picking commit 9c3144e28.
  (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:
	renamed:    runtime/src/serde_snapshot/future.rs -> runtime/src/serde_snapshot/newer.rs
	modified:   runtime/src/serde_snapshot/tests.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   runtime/src/serde_snapshot.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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[solana-grimes]

😱 New commits were pushed while the automerge label was present.

[github-actions]

This PR has been automatically locked since there has not been any activity in past 14 days after it was merged.