Feeds: Don't override the Content-Type header inside `fetch_feed()`.

SimplePie can set the Content-Type header automatically with the correct charset for convenience, but we already force the charset to match the site's, making it redundant at best. At worst, SimplePie incorrectly overrides the content-type for non-HTML content (such as API requests).

Props dlh, stevenkword, rmccue.
Merges [39681] to the 4.7 branch.
Fixes #39066.

Built from https://develop.svn.wordpress.org/branches/4.7@39683


git-svn-id: http://core.svn.wordpress.org/branches/4.7@39623 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/feed.php

@@ -702,7 +702,6 @@ function fetch_feed( $url ) {
 	do_action_ref_array( 'wp_feed_options', array( &$feed, $url ) );
 	$feed->init();
 	$feed->set_output_encoding( get_option( 'blog_charset' ) );
-	$feed->handle_content_type();
 
 	if ( $feed->error() )
 		return new WP_Error( 'simplepie-error', $feed->error() );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7.1-alpha-39682';
+$wp_version = '4.7.1-alpha-39683';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.