[turbofan] Enable debugger test that no longer fails.

R=bmeurer@chromium.org
TEST=mjsunit/debug-referenced-by
BUG=v8:4754

Review-Url: https://codereview.chromium.org/2225803002
Cr-Commit-Position: refs/heads/master@{#38431}

test/mjsunit/mjsunit.status

@@ -338,9 +338,6 @@
   # BUG(v8:3097)
   'debug-references': [SKIP],
 
-  # BUG(v8:4754).
-  'debug-referenced-by': [PASS, NO_VARIANTS],
-
   # BUG(v8:4779): Crashes flakily with stress mode on arm64.
   'array-splice': [PASS, SLOW, ['arch == arm64', FAST_VARIANTS]],