test: fix flaky watchFile()

The regression that test-fs-watch-file-enoent-after-deletion was written
to test for involves whether or not the callback runs or not. Checking
what the file watcher reports unfortunately is subject to race
conditions on Windows (and possibly elsewhere) because the file watcher
returns control to the event loop before it may be receiving data from
the OS. So remove those assertions. The test still checks what it is
supposed to check, but is no longer subject to race conditions.

Fixes: https://github.com/nodejs/node/issues/21692

PR-URL: https://github.com/nodejs/node/pull/21694


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>