Harden set-default Checkout in e2e-versions.yml (persist-credentials: false)

The Checkout step in the set-default option job was the only one of 17
checkout steps in the workflow missing persist-credentials: false,
flagged by zizmor's artipacked audit. Align it with the rest of the file.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

.github/workflows/e2e-versions.yml

@@ -704,6 +704,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v7
+        with:
+          persist-credentials: false
       - name: Setup Java 17 as default
         uses: ./
         id: setup-java-17
@@ -757,16 +759,16 @@ jobs:
         shell: pwsh
       - name: Verify Java 21 outputs are set
         env:
-          JAVA21_PATH: ${{ steps.setup-java-21.outputs.path }}
-          JAVA21_VERSION: ${{ steps.setup-java-21.outputs.version }}
+          JAVA_21_PATH: ${{ steps.setup-java-21.outputs.path }}
+          JAVA_21_VERSION: ${{ steps.setup-java-21.outputs.version }}
         run: |
-          echo "Java 21 path=$JAVA21_PATH"
-          echo "Java 21 version=$JAVA21_VERSION"
-          if [ -z "$JAVA21_PATH" ]; then
+          echo "Java 21 path=$JAVA_21_PATH"
+          echo "Java 21 version=$JAVA_21_VERSION"
+          if [ -z "$JAVA_21_PATH" ]; then
             echo "Java 21 path output should be set"
             exit 1
           fi
-          if [ -z "$JAVA21_VERSION" ]; then
+          if [ -z "$JAVA_21_VERSION" ]; then
             echo "Java 21 version output should be set"
             exit 1
           fi