Update known wrapper checksums (#488)

Automatically generated pull request to update the known wrapper
checksums.

In case of conflicts, manually run the workflow from the [Actions
tab](https://github.com/gradle/actions/actions/workflows/update-checksums-file.yml),
the changes will then be force-pushed onto this pull request branch.
Do not manually update the pull request branch; those changes might get
overwritten.

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Co-authored-by: bigdaz <179734+bigdaz@users.noreply.github.com>

sources/src/wrapper-validation/wrapper-checksums.json

@@ -1,4 +1,8 @@
 [
+  {
+    "version": "8.12-rc-2",
+    "checksum": "2db75c40782f5e8ba1fc278a5574bab070adccb2d21ca5a6e5ed840888448046"
+  },
   {
     "version": "8.12-rc-1",
     "checksum": "2db75c40782f5e8ba1fc278a5574bab070adccb2d21ca5a6e5ed840888448046"