Fix the unit test.

tests/phpunit/tests/rest-api/wpRestTemplatesController.php

@@ -288,7 +288,7 @@ public function test_get_item() {
 	 */
 	public function test_get_item_should_return_no_response_body_for_head_requests() {
 		wp_set_current_user( self::$admin_id );
-		$request  = new WP_REST_Request( 'GET', '/wp/v2/templates/default//my_template' );
+		$request  = new WP_REST_Request( 'HEAD', '/wp/v2/templates/default//my_template' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertSame( 200, $response->get_status(), 'Response status is 200.' );
 		$this->assertNull( $response->get_data(), 'The server should not generate a body in response to a HEAD request.' );