Docs: Correct the `@return` type of `get_theme_mod()`.

This now matches the type of the `$value` parameter of `set_theme_mod()`.

Props mensmaximus.
Fixes #45319.


Built from https://develop.svn.wordpress.org/trunk@44613


git-svn-id: http://core.svn.wordpress.org/trunk@44444 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/theme.php

@@ -890,7 +890,7 @@ function get_theme_mods() {
  *
  * @param string      $name    Theme modification name.
  * @param bool|string $default
- * @return string
+ * @return mixed
  */
 function get_theme_mod( $name, $default = false ) {
 	$mods = get_theme_mods();

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-beta1-44612';
+$wp_version = '5.1-beta1-44613';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.