Use prefix increment consistent with the rest of the method

Author: sirreal

src/wp-includes/html-api/class-wp-html-tag-processor.php

@@ -1433,7 +1433,7 @@ private function skip_script_data(): bool {
 
 			// Everything of interest past here starts with "<".
 			if ( $at + 1 >= $doc_length || '<' !== $html[ $at + 1 ] ) {
-				$at += 1;
+				++$at;
 				continue;
 			}