GHA Linux builder: do not log out from ghcr

Although there is only one job running at a time,
but this looks safer, still.

[ci skip]

.github/workflows/linux-builder-containers.yaml

@@ -77,6 +77,7 @@ jobs:
         registry: ghcr.io
         username: ${{ github.repository_owner }}
         password: ${{ secrets.GITHUB_TOKEN }}
+        logout: false
 
     - name: Build
       run: |