[mjsunit] Simplify log test to avoid timer issues

Avoid --log-all which activates profiling timers that have issues on
certain bots. --log-code is good enough to test whether logging works.

Bug: v8:10937
Change-Id: I3284801f7b423480756abb0f3c33980a9776575d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2424349Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70093}

test/mjsunit/tools/log.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --logfile='+' --log-all --log --no-stress-opt
+// Flags: --logfile='+' --log --log-code --no-stress-opt
 
 function testFunctionWithFunnyName(o) {
   return o.a;