Move Gradle wrapper validator action to own workflow

It fails too much!  Copied from cashapp/molecule.

.github/workflows/build.yml

@@ -23,9 +23,6 @@ jobs:
       - name: Checkout
         uses: actions/[email protected]
 
-      - name: Validate Gradle Wrapper
-        uses: gradle/[email protected]
-
       - name: Configure JDK
         uses: actions/setup-java@v3
         with:

.github/workflows/gradle-wrapper.yml

@@ -0,0 +1,18 @@
+name: gradle-wrapper
+
+on:
+  pull_request:
+    paths:
+      - 'gradlew'
+      - 'gradlew.bat'
+      - 'gradle/wrapper/'
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Validate Gradle Wrapper
+        uses: gradle/wrapper-validation-action@v1