[infra] Bump shards on slow bots

No-Try: true
Bug: chromium:1337252
Change-Id: I6c4f17a2ddea72996dc48411a8245380da979b2f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3711755
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Alexander Schulze <alexschulze@chromium.org>
Reviewed-by: Alexander Schulze <alexschulze@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81233}

infra/testing/builders.pyl

@@ -715,7 +715,7 @@
     },
     'tests': [
       {'name': 'mozilla'},
-      {'name': 'test262', 'variant': 'default', 'shards': 2},
+      {'name': 'test262', 'variant': 'default', 'shards': 4},
       {'name': 'v8testing', 'shards': 3},
       {'name': 'v8testing', 'variant': 'extra', 'shards': 2},
     ],
@@ -727,7 +727,7 @@
     },
     'tests': [
       {'name': 'mozilla'},
-      {'name': 'test262', 'variant': 'default'},
+      {'name': 'test262', 'variant': 'default', 'shards': 2},
       {'name': 'v8testing', 'shards': 2},
     ],
   },
@@ -738,7 +738,7 @@
     },
     'tests': [
       {'name': 'mozilla'},
-      {'name': 'test262', 'variant': 'default'},
+      {'name': 'test262', 'variant': 'default', 'shards': 2},
       {'name': 'v8testing', 'shards': 2},
       {'name': 'v8testing', 'variant': 'extra'},
     ],
@@ -1625,7 +1625,7 @@
     },
     'tests': [
       {'name': 'mozilla'},
-      {'name': 'test262', 'variant': 'default'},
+      {'name': 'test262', 'variant': 'default', 'shards': 2},
       {'name': 'v8testing', 'shards': 4},
       {'name': 'v8testing', 'variant': 'extra', 'shards': 3},
     ],