chore(spelling): improve info about used commit on init/update

scripts/rcstack/rcstack

@@ -296,13 +296,13 b' rcstack_self_update_usage() {'
 
     # :flag.usage
     printf "  %s\n" "--cli-revision CLI_REVISION"
-    printf "    revision to fetch new rcstack cli tool.\n"
+    printf "    commit or branch to fetch new rcstack cli tool.\n"
     printf "    Default: master\n"
     echo
 
     # :flag.usage
     printf "  %s\n" "--docker-revision DOCKER_REVISION"
-    printf "    revision to fetch new docker definitions.\n"
+    printf "    commit or branch to fetch new docker definitions.\n"
     printf "    Default: master\n"
     echo