Coding Standards: Remove unnecessary `isset()` from `xmlrpc.php`.

This removes a redundant `isset( $HTTP_RAW_POST_DATA )` from `xmlrpc.php`, as the variable is already set in the code block immediately preceding the affected line.

Follow-up to [3498], [5445], [47926].

Props justlevine.
See #52217.
Built from https://develop.svn.wordpress.org/trunk@59376


git-svn-id: http://core.svn.wordpress.org/trunk@58762 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.8-alpha-59374';
+$wp_version = '6.8-alpha-59376';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

xmlrpc.php

@@ -22,9 +22,7 @@ if ( ! isset( $HTTP_RAW_POST_DATA ) ) {
 }
 
 // Fix for mozBlog and other cases where '<?xml' isn't on the very first line.
-if ( isset( $HTTP_RAW_POST_DATA ) ) {
 $HTTP_RAW_POST_DATA = trim( $HTTP_RAW_POST_DATA );
-}
 // phpcs:enable
 
 /** Include the bootstrap for setting up WordPress environment */