[infra] increase shards for v8_linux_rel_ng

This CL speeds up one of the slowest builders on the CQ to improve overall CQ time.

R=machenbach@chromium.org,liviurau@chromium.org,alexschulze@chromium.org

Bug: v8:12810
Change-Id: I80adfb3abdea1ef7e14abf0a8c2dc2cc2b4d77d9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3593134
Auto-Submit: Tamer Tas <tmrts@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80039}

infra/testing/builders.pyl

@@ -156,10 +156,10 @@
       {'name': 'mozilla', 'variant': 'extra'},
       {'name': 'optimize_for_size'},
       {'name': 'test262', 'shards': 4},
-      {'name': 'test262', 'variant': 'extra', 'shards': 3},
-      {'name': 'v8testing', 'shards': 2},
-      {'name': 'v8testing', 'suffix': 'isolates', 'test_args': ['--isolates'], 'shards': 2},
-      {'name': 'v8testing', 'variant': 'extra', 'shards': 2},
+      {'name': 'test262', 'variant': 'extra', 'shards': 6},
+      {'name': 'v8testing', 'shards': 4},
+      {'name': 'v8testing', 'suffix': 'isolates', 'test_args': ['--isolates'], 'shards': 4},
+      {'name': 'v8testing', 'variant': 'extra', 'shards': 4},
     ],
   },
   'v8_linux_optional_rel_ng_triggered': {