Add 'tests/tail/pipe-f' to ignore list

Author: sylvestre

.github/workflows/ignore-intermittent.txt

@@ -6,6 +6,7 @@ tests/pr/bounded-memory
 tests/tail/inotify-dir-recreate
 tests/tail/overlay-headers
 tests/tail/tail-n0f
+tests/tail/pipe-f
 tests/timeout/timeout
 tests/tail/symlink
 tests/shuf/shuf-reservoir