Build/Test Tools: Update several NPM packages.

This updates the following packages to the latest versions. 

Updated packages:
- `grunt-contrib-uglify` from `4.0.1` to `5.0.0`.
- `grunt-jsdoc` from `2.4.0` to `2.4.1`.
- `grunt-legacy-util` from `1.1.1` to `2.0.0`.
- `grunt-webpack` from `3.1.3` to `4.0.2`.

See #51801.
Built from https://develop.svn.wordpress.org/trunk@49933


git-svn-id: http://core.svn.wordpress.org/trunk@49632 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7-alpha-49932';
+$wp_version = '5.7-alpha-49933';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.