Remove the second space after a period in WordPress posts

gistfile1.php

// See: http://www.jetmore.org/john/blog/2012/03/multiple-spaces-after-period-in-wordpress/
function gist_kill_double_space( $content ) {
	if ( seems_utf8( $content ) ) {
		$clean_content = preg_replace( '/[\p{Z}\s]{2,}/u', ' ', $content );
	} else {
		$clean_content = preg_replace( '/\s\s+/', ' ', $content );
	}
	return $clean_content;
}
add_filter( 'the_content', 'gist_kill_double_space' );