CI: disable persist-credentials for actions/checkout

It is a possible security issue.
We do not want to persist credentials in the repo and thus exposing those
to further steps.

References:

actions/checkout#485 (comment)
azat/chdig#67

.github/workflows/ci.yml

@@ -25,6 +25,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+        with:
+          persist-credentials: false
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v2