Remove experimental to experimental upgrade test (operator-framework#2518)

Signed-off-by: Per G. da Silva <pegoncal@redhat.com>
Co-authored-by: Per G. da Silva <pegoncal@redhat.com>

Author: perdasilva

.github/workflows/e2e.yaml

@@ -31,10 +31,6 @@ jobs:
             make-target: test-upgrade-st2st-e2e
             use-artifacts: true
             use-codecov: false
-          - name: upgrade-ex2ex-e2e
-            make-target: test-upgrade-ex2ex-e2e
-            use-artifacts: true
-            use-codecov: false
           - name: upgrade-st2ex-e2e
             make-target: test-upgrade-st2ex-e2e
             use-artifacts: true