using hash for checkout action

Author: l-trotta

.github/workflows/release_central.yml

@@ -35,7 +35,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
         with:
           ref: ${{ inputs.branch }}
           fetch-depth: '1'
@@ -76,7 +76,7 @@ jobs:
           vault-instance: "ci-prod"
 
       - name: Tag branch ${{ inputs.branch }} with release ${{ inputs.version }}, bump version with new release ${{ inputs.version }}
-        uses: actions/checkout@v7 // TODO commit hash
+        uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
         with:
           repository: elastic/elasticsearch-java
           token: ${{ steps.fetch-ephemeral-token.outputs.token }}