[test] Bump shards for slow test step

Test262 with extra variants times out on several debug bots regularly:
https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20-%20debug/37382
https://ci.chromium.org/p/v8/builders/ci/V8%20Linux%20-%20debug/35401
https://ci.chromium.org/p/v8/builders/try.triggered/v8_linux64_dbg_ng_triggered/b8845063257835477664

Bug: v8:11428
Change-Id: I749556be0e5dd5ce788ee66ba10e1431ebf47b93
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2944938
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74997}

infra/testing/builders.pyl

@@ -77,7 +77,7 @@
       {'name': 'mozilla'},
       {'name': 'mozilla', 'variant': 'extra'},
       {'name': 'test262', 'variant': 'default', 'shards': 2},
-      {'name': 'test262', 'variant': 'extra', 'shards': 3},
+      {'name': 'test262', 'variant': 'extra', 'shards': 5},
       {'name': 'v8testing', 'shards': 3},
       {'name': 'v8testing', 'variant': 'extra', 'shards': 2},
       # Noavx.
@@ -347,7 +347,7 @@
       {'name': 'mozilla'},
       {'name': 'mozilla', 'variant': 'extra'},
       {'name': 'test262', 'variant': 'default'},
-      {'name': 'test262', 'variant': 'extra', 'shards': 3},
+      {'name': 'test262', 'variant': 'extra', 'shards': 5},
       {'name': 'v8testing', 'shards': 3},
       {'name': 'v8testing', 'variant': 'extra', 'shards': 3},
       {'name': 'v8testing', 'variant': 'minor_mc'},
@@ -935,7 +935,7 @@
       {'name': 'optimize_for_size'},
       {'name': 'test262', 'shards': 6},
       {'name': 'test262', 'variant': 'code_serializer', 'shards': 2},
-      {'name': 'test262', 'variant': 'extra', 'shards': 3},
+      {'name': 'test262', 'variant': 'extra', 'shards': 5},
       {'name': 'v8testing', 'shards': 3},
       {
         'name': 'v8testing',
@@ -1168,7 +1168,7 @@
       {'name': 'mozilla', 'variant': 'extra'},
       {'name': 'optimize_for_size'},
       {'name': 'test262', 'shards': 5},
-      {'name': 'test262', 'variant': 'extra', 'shards': 3},
+      {'name': 'test262', 'variant': 'extra', 'shards': 5},
       {'name': 'v8testing', 'shards': 2},
       {'name': 'v8testing', 'variant': 'extra', 'shards': 2},
       {'name': 'v8testing', 'variant': 'minor_mc'},