fuzz_date: skip combined short options like -Rf- that read from stdin

[ChrisDryden]

This is a very minor fix for the fuzzing for date where some random args will read data from stdin. This issue has come up twice for me in the CI recently.

Fixes: #9783

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/shuf/shuf-reservoir (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/sort/sort-stale-thread-mem (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)