Increase shards for Mac on ARM64 buiders

Bug: chromium:1126467
Change-Id: Id10117b99fa28504780dd6c0a7850bb17e5e94ef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2414210
Auto-Submit: Almothana Athamneh <almuthanna@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69957}

infra/testing/builders.pyl

@@ -668,7 +668,7 @@
       'os': 'Mac-10.13',
     },
     'tests': [
-      {'name': 'v8testing', 'shards': 3},
+      {'name': 'v8testing', 'shards': 8},
     ],
   },
   'v8_mac_arm64_sim_dbg_ng_triggered': {
@@ -677,7 +677,7 @@
       'os': 'Mac-10.13',
     },
     'tests': [
-      {'name': 'v8testing', 'shards': 3},
+      {'name': 'v8testing', 'shards': 8},
     ],
   },
   'v8_mac_arm64_sim_nodcheck_rel_ng_triggered': {
@@ -686,7 +686,7 @@
       'os': 'Mac-10.13',
     },
     'tests': [
-      {'name': 'v8testing', 'shards': 3},
+      {'name': 'v8testing', 'shards': 8},
     ],
   },
   ##############################################################################
@@ -1271,7 +1271,7 @@
       'priority': 35,
     },
     'tests': [
-      {'name': 'v8testing', 'shards': 3},
+      {'name': 'v8testing', 'shards': 8},
     ],
   },
   'V8 Mac - arm64 - sim - release': {
@@ -1285,7 +1285,7 @@
       'priority': 35,
     },
     'tests': [
-      {'name': 'v8testing', 'shards': 3},
+      {'name': 'v8testing', 'shards': 8},
     ],
   },
   'V8 Win32': {