Bundled Themes: Update several package versions in Twenty Twenty and Twenty Nineteen.

The following packages received version bumps:

Twenty Twenty
- `concurrently`
- `postcss-cli`
- `rtlcss`
- `stylelint-a11y`

Twenty Nineteen
- `node-sass`
- `postcss-cli`
- `rtlcss`

See #49768.
Built from https://develop.svn.wordpress.org/trunk@47925


git-svn-id: http://core.svn.wordpress.org/trunk@47699 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47924';
+$wp_version = '5.5-alpha-47925';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.