realpath: remove to_string_lossy

[oech3]

to_string_lossy is overkill just for checking that it ends with a valid unicode bytes.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.
Note: The gnu test tests/env/env-signal-handler was skipped on 'main' but is now failing.

[cakebaker]

Thanks!