Revert "Add Gradle Wrapper Validation GitHub Action"

This reverts commit 136cdacb40.

Our GitHub billing plan does not support Actions at the moment.
Reverting until that has been resolved.

See gh-19762

.github/workflows/gradle-wrapper-validation.yml

@@ -1,10 +0,0 @@
-name: "Validate Gradle Wrapper"
-on: [push, pull_request]
-
-jobs:
-  validation:
-    name: "Validation"
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - uses: gradle/wrapper-validation-action@v1