Updating Twenty Nineteen, the new default theme for 2019.

This update changes the following:

- Reverts the customization to the toolbar for wide and full blocks to make them more usable. More info here: https://github.com/WordPress/twentynineteen/pull/668
- Add `nowrap` to the columns block at breakpoints above `600px`. More info here: https://github.com/WordPress/twentynineteen/pull/674 

Props joen, kjellr, allancole.

Fixes #45369.

Merges [44189] into trunk.

See #45424.
Built from https://develop.svn.wordpress.org/trunk@44300


git-svn-id: http://core.svn.wordpress.org/trunk@44130 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44299';
+$wp_version = '5.1-alpha-44300';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.