Revert "[infra] Add gc_stats variant to Linux64 debug bot"

This reverts commit e839484e.

Reason for revert: https://ci.chromium.org/buildbot/client.v8/V8%20Linux64%20-%20debug/22300

Original change's description:
> [infra] Add gc_stats variant to Linux64 debug bot
> 
> No-try: true
> Bug: v8:7760
> Change-Id: I2a4e91b58de4387a4bfa5b79681db25880af8954
> Reviewed-on: https://chromium-review.googlesource.com/1068643
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#53394}

TBR=machenbach@chromium.org,mlippautz@chromium.org

Change-Id: I7342341fb63742de4e51c0df65e8323f2a6dbd7a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7760
Reviewed-on: https://chromium-review.googlesource.com/1075927Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53395}

infra/testing/builders.pyl

@@ -397,7 +397,6 @@
   },
   'V8 Linux64 - debug': {
     'tests': [
-      {'name': 'v8testing', 'variant': 'gc_stats', 'shards': 1},
       {'name': 'v8testing', 'variant': 'minor_mc', 'shards': 1},
       {'name': 'v8testing', 'variant': 'slow_path', 'shards': 1},
     ],

test/cctest/test-global-object.cc

@@ -59,9 +59,6 @@ TEST(KeysGlobalObject_Regress2764) {
   LocalContext env1;
   v8::HandleScope scope(env1->GetIsolate());
 
-  // Installing an extensions change the global object.
-  if (i::FLAG_gc_stats) return;
-
   // Create second environment.
   v8::Local<Context> env2 = Context::New(env1->GetIsolate());