test: remove flaky status for test-statwatcher

test-statwatcher does not appear to be failing anymore in CI. Remove
"flaky" status for the test.

Closes: https://github.com/nodejs/node/issues/21425

PR-URL: https://github.com/nodejs/node/pull/29392
Fixes: https://github.com/nodejs/node/issues/21425


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>