ci/prow-entrypoint: drop "build"/"init-and-build-default" verbs

This has been around for a while but isn't used anywhere AFAICT. Just
nuke it.

Author: jlebon

ci/prow-entrypoint.sh

@@ -270,10 +270,6 @@ main() {
             cosa_init "$2"
             prepare_repos
             ;;
-        "build" | "init-and-build-default")  # TODO: change prow job to use init-and-build-default
-            cosa_init "ocp-rhel-9.6"
-            cosa_build
-            ;;
         # this is called by cosa's CI
         "rhcos-cosa-prow-pr-ci")
             setup_user