Revert "Override _runner_flags for num_fuzzer.py"

This reverts commit 3927c9c4.

Reason for revert:
https://ci.chromium.org/p/v8/builders/ci/V8%20NumFuzz%20-%20debug/10732

Original change's description:
> Override _runner_flags for num_fuzzer.py
> 
> This CL ensures that we add the
> '--fuzzing' flag to the num_fuzzer script.
> Please note that NumFuzzer does not inherit the
> StandardTestRunner class but it inherits
> BaseTestRunner so we had to override _runner_flags.
> 
> Bug: v8:10755
> Change-Id: Ifb779ba402106b8f2ce4d0e13090ef2db468a6ae
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2335185
> Commit-Queue: Almothana Athamneh <almuthanna@chromium.org>
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Reviewed-by: Liviu Rau <liviurau@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#69241}

TBR=machenbach@chromium.org,liviurau@chromium.org,almuthanna@chromium.org

Change-Id: Ie39fb87a0e53c5cbbc276f8efb6e4a89ce44bb74
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10755
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2340902Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69255}

tools/testrunner/num_fuzzer.py

@@ -117,10 +117,6 @@ class NumFuzzer(base_runner.BaseTestRunner):
   def _get_default_suite_names(self):
     return DEFAULT_SUITES
 
-  def _runner_flags(self):
-    """Extra default flags specific to the test runner implementation."""
-    return ['--fuzzing']
-
   def _get_statusfile_variables(self, options):
     variables = (
         super(NumFuzzer, self)._get_statusfile_variables(options))