uucore: remove unused getpid and getsid functions

[xtqqczze]

No description provided.

[sylvestre]

are you sure it isn't used by other consumers of uucore ?

[xtqqczze]

are you sure it isn't used by other consumers of uucore ?

nushell depends on uucore crate but not these functions, but other coreutils repos do:

https://github.com/uutils/procps/blob/4ebf73c7129c4ef637f2551690e8d72b861ff4f0/src/uu/pgrep/src/process.rs#L494

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/misc/io-errors is no longer failing!
Congrats! The gnu test tests/timeout/timeout-group is no longer failing!
Congrats! The gnu test tests/tail/tail-n0f is now passing!