ci(ct-base): limit base image build to IQSS upstream

Avoids unnecessary tries to push things when people develop in their
forked repos.

.github/workflows/container_base_push.yml

@@ -26,6 +26,7 @@ jobs:
         strategy:
             matrix:
                 jdk: [ '11' ]
+        if: ${{ github.repository_owner == 'IQSS' }}
 
         steps:
             - name: Checkout repository