refs #21603 [finc] use separate task for grunt manual

Gruntfile.js

@@ -245,7 +245,7 @@ module.exports = function(grunt) {
   });
   grunt.registerTask('default', ['scss']);
 
-  grunt.registerTask('default', function help() {
+  grunt.registerTask('help', function help() {
     grunt.log.writeln(`\nHello! Here are your grunt command options:
 
     - grunt less        = compile and compress all themes' LESS files to css.