Reland "[heap] Fix typo in field trial config"

This is a reland of commit 5bdf1b1

Original change's description:
> [heap] Fix typo in field trial config
>
> Bug: v8:12612
> Change-Id: I97bacde636e123fc0d7fb7824fc307e1f1128a52
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4846589
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Auto-Submit: Omer Katz <omerkatz@chromium.org>
> Commit-Queue: Omer Katz <omerkatz@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1193660}

Bug: v8:12612
Change-Id: Ibda548f984105354354375e82f0fe365759a5908
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4855983
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1195063}

testing/variations/fieldtrial_testing_config.json

@@ -17661,7 +17661,7 @@
                 {
                     "name": "Enabled",
                     "enable_features": [
-                        "kV8MinorMS"
+                        "V8MinorMS"
                     ]
                 }
             ]