Docs: Avoid using “CPT” instead of “custom post type”.

Additionally, when referring to built in Core post types, “custom” is unnecessary.

This also adds a period to the end of the `wp_global_styles` post type description.

Follow up to [38829], [51003], [52041], [52049], [52062].

See #53399, #54335, #54336.

git-svn-id: https://develop.svn.wordpress.org/trunk@52110 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/theme.php

@@ -1913,7 +1913,7 @@ function wp_get_custom_css( $stylesheet = '' ) {
 	 *
 	 * @since 4.7.0
 	 *
-	 * @param string $css        CSS pulled in from the Custom CSS CPT.
+	 * @param string $css        CSS pulled in from the Custom CSS post type.
 	 * @param string $stylesheet The theme stylesheet name.
 	 */
 	$css = apply_filters( 'wp_get_custom_css', $css, $stylesheet );