Build Tools: Update the preserveComments option for uglify:jqueryui.

Uglify2 doesn't support the value "some" anymore. Replace it with the `/^!/` regex which produces the same output as before.

See https://build.trac.wordpress.org/changeset/35502 and https://build.trac.wordpress.org/changeset/35528.
Fixes #34177.

git-svn-id: https://develop.svn.wordpress.org/trunk@35564 602fd350-edb4-49c9-b593-d223f7449a82

Gruntfile.js

@@ -451,7 +451,8 @@ module.exports = function(grunt) {
 			},
 			jqueryui: {
 				options: {
-					preserveComments: 'some'
+					// Preserve comments that start with a bang.
+					preserveComments: /^!/
 				},
 				expand: true,
 				cwd: SOURCE_DIR,