Favicon: Do not specify a Content-Length: 0 header for our "empty" response to fail more gracefully on environments with extra whitespace on output.

This allows for the web server to generate the appropriate `Content-Length` header for the request, allowing for strict clients/proxies/servers to process the response.

Props swissspidy.
Fixes #33626


git-svn-id: https://develop.svn.wordpress.org/trunk@33935 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/load.php

@@ -132,7 +132,6 @@ function wp_check_php_mysql_versions() {
 function wp_favicon_request() {
 	if ( '/favicon.ico' == $_SERVER['REQUEST_URI'] ) {
 		header('Content-Type: image/vnd.microsoft.icon');
-		header('Content-Length: 0');
 		exit;
 	}
 }