Remove kubectl exception in container scanning

Because we now have a builtin kubectl, we don't need that
security exception.

.github/containerscan/allowedlist.yaml

@@ -1,7 +0,0 @@
-general:
-  bestPracticeViolations:
-    # We violate this rule because we add kubectl from a remote location
-    # Instead of building it from source/copying it.
-    # Until we change our practices (e.g. have Dockerfile build kubectl
-    # in a multi-staged manner), we should skip this check
-    - CIS-DI-0009