Skip slow test regress-779407 in experimental_regexp variant

The experimental engine struggles to compile this large pattern.

Change-Id: I0abd5c7ed9f6f62b1c18b5c3dc1cb6a25e130c53
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2712754
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72941}

test/mjsunit/mjsunit.status

@@ -1466,4 +1466,9 @@
   'baseline/*': [SKIP],
 }],
 
+##############################################################################
+['variant == experimental_regexp', {
+  'regress/regress-779407': [SKIP],
+}],  # variant == experimental_regexp
+
 ]