[infra] Remove gpu dimension from mac bots.

Bug: chromium:1279426
Change-Id: Ia510b105a4aacbca3abc521b110bcf58cfe6e294
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3335816
Auto-Submit: Alexander Schulze <alexschulze@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78355}

infra/testing/builders.pyl

@@ -822,7 +822,6 @@
     'swarming_dimensions' : {
       'cpu': 'x86-64',
       'os': 'Mac-10.15',
-      'gpu': 'none',
     },
     'tests': [
       {'name': 'v8testing', 'shards': 8},
@@ -833,7 +832,6 @@
     'swarming_dimensions' : {
       'cpu': 'x86-64',
       'os': 'Mac-10.15',
-      'gpu': 'none',
     },
     'tests': [
       {'name': 'v8testing', 'shards': 8},
@@ -844,7 +842,6 @@
     'swarming_dimensions' : {
       'cpu': 'x86-64',
       'os': 'Mac-10.15',
-      'gpu': 'none',
     },
     'tests': [
       {'name': 'v8testing', 'shards': 8},
@@ -1571,7 +1568,6 @@
     'swarming_dimensions' : {
       'cpu': 'x86-64',
       'os': 'Mac-10.15',
-      'gpu': 'none',
     },
     'swarming_task_attrs': {
       'expiration': 14400,
@@ -1587,7 +1583,6 @@
     'swarming_dimensions' : {
       'cpu': 'x86-64',
       'os': 'Mac-10.15',
-      'gpu': 'none',
     },
     'swarming_task_attrs': {
       'expiration': 14400,