uucore: pipes.rs replace != with >

[oech3]

!= is too strict. Might cause infinite loop if external crate has a bug.

[github-actions]

GNU testsuite comparison:

Note: The gnu test tests/rm/many-dir-entries-vs-OOM is now being skipped but was previously passing.
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Skip an intermittent issue tests/pr/bounded-memory (was skipped on 'main', now failing)

[cakebaker]

Thanks!