Remove return types.

src/wp-includes/functions.php

@@ -4711,7 +4711,7 @@ function _mce_set_direction( $mce_init ) {
  *
  * @return bool True if it's a WordPress REST API request, false otherwise.
  */
-function wp_is_serving_rest_request(): bool {
+function wp_is_serving_rest_request() {
 	return defined( 'REST_REQUEST' ) && REST_REQUEST;
 }
 

src/wp-includes/rest-api.php

@@ -3401,7 +3401,7 @@ static function ( $status, $error_data ) {
  *
  * @return bool True if a REST endpoint request is currently being handled, false otherwise.
  */
-function wp_is_rest_endpoint(): bool {
+function wp_is_rest_endpoint() {
 	/* @var WP_REST_Server $wp_rest_server */
 	global $wp_rest_server;
 

src/wp-includes/rest-api/class-wp-rest-server.php

@@ -1067,7 +1067,7 @@ public function dispatch( $request ) {
 	 *
 	 * @return bool Whether the REST server is currently handling a request.
 	 */
-	public function is_dispatching(): bool {
+	public function is_dispatching() {
 		return empty( $this->dispatching_requests );
 	}