ci: pin github actions to commit hash

Author: kruton

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

@@ -13,5 +13,5 @@ jobs:
     name: "Validation"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: gradle/wrapper-validation-action@v2
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - uses: gradle/wrapper-validation-action@f9c9c575b8b21b6485636a91ffecd10e558c62f6 # v3.5.0