tail: increase retry delay and sleep interval for flaky test

[mattsu2020]

Summary

Increases the retry delay from 100ms to 400ms and sleep interval from 0.1s to 0.2s in test_retry9 to address flaky test behavior caused by timing sensitivity.

[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/date/resolution (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/tail/pipe-f is now being skipped but was previously passing.
Congrats! The gnu test tests/pr/bounded-memory is now passing!
Congrats! The gnu test tests/tail/tail-n0f is now passing!