Do not use cache when building containers in GitHub workflow (#infra)

We are setting CONTAINER_BUILD_ARGS env variable in Fedora which was also
brought here. The problem is that CONTAINER_BUILD_ARGS are also Makefile
variable so instead of having the default value which is "--no-cache" we will
set an empty string which will enable the cache back.

We don't use this env variable on RHEL so it's safe for removal.

.github/workflows/tests.yml

@@ -24,7 +24,6 @@ jobs:
             ci_tag: 'rhel-9'
     env:
       CI_TAG: '${{ matrix.ci_tag }}'
-      CONTAINER_BUILD_ARGS: '${{ matrix.build-args }}'
       TARGET_BRANCH_NAME: 'origin/${{ matrix.target_branch }}'
 
     steps:
@@ -73,7 +72,6 @@ jobs:
             ci_tag: 'rhel-9'
     env:
       CI_TAG: '${{ matrix.ci_tag }}'
-      CONTAINER_BUILD_ARGS: '${{ matrix.build-args }}'
       TARGET_BRANCH_NAME: 'origin/${{ matrix.target_branch }}'
 
     steps: