[test] Mark slow tests

No-try: true
Bug: v8:11784
Change-Id: I7d40cbead84d27a7783d3e05eeedcc8ea7597bc0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2903151
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74636}

test/mjsunit/mjsunit.status

@@ -599,6 +599,7 @@
   # Slow tests.
   'compiler/regress-1125145': [SKIP],
   'compiler/regress-crbug-11564': [PASS, SLOW],
+  'd8/d8-worker-shutdown*': [PASS, SLOW],
   'es6/block-conflicts-sloppy': [PASS, SLOW],
   'math-floor-part1': [PASS, SLOW],
   'regress/regress-430201': [SKIP],