log: remove --log-regexp from comments

--log-regexp was removed in
https://codereview.chromium.org/2422593003. This commit removes
references to that flag in src/logging/log.h.

Change-Id: Idc965f06dd1f85370b5391c495ae113306655b75
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2646246Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/master@{#72361}

src/logging/log.h

@@ -35,7 +35,7 @@ struct TickSample;
 //
 // --log-all
 // Log all events to the file, default is off.  This is the same as combining
-// --log-api, --log-code, and --log-regexp.
+// --log-api and --log-code.
 //
 // --log-api
 // Log API events to the logfile, default is off.  --log-api implies --log.
@@ -44,10 +44,6 @@ struct TickSample;
 // Log code (create, move, and delete) events to the logfile, default is off.
 // --log-code implies --log.
 //
-// --log-regexp
-// Log creation and use of regular expressions, Default is off.
-// --log-regexp implies --log.
-//
 // --logfile <filename>
 // Specify the name of the logfile, default is "v8.log".
 //