Bump the $wp_version.

This version string controls more than you might first imagine, but the important thing to note for now, is that this needs to contain a revision number in order for nightly builds to include a revision number.
If a nightly build doesn't include a revision number, Background Updates won't occur for Development users (after all, 4.1-beta1 == 4.1-beta1, which is already installed).
See #30405

Built from https://develop.svn.wordpress.org/trunk@30411


git-svn-id: http://core.svn.wordpress.org/trunk@30406 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.1-beta1';
+$wp_version = '4.1-beta1-30411';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.