Doubling number of shards for 'test262 extra' on 'V8 Linux64'

Bug: v8:12538
Change-Id: I4f1d4bc33846c158044da76b882d54469ff031a4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3377124
Commit-Queue: Almothana Athamneh <almuthanna@chromium.org>
Auto-Submit: Almothana Athamneh <almuthanna@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78543}

infra/testing/builders.pyl

@@ -1145,7 +1145,7 @@
       {'name': 'perf_integration'},
       {'name': 'test262', 'shards': 2},
       {'name': 'test262', 'variant': 'assert_types'},
-      {'name': 'test262', 'variant': 'extra'},
+      {'name': 'test262', 'variant': 'extra', 'shards': 2},
       {'name': 'v8initializers'},
       {'name': 'v8testing'},
       {'name': 'v8testing', 'variant': 'assert_types'},