Update by.js: Add forgotten RelativeBy in check options (#12289)

javascript/node/selenium-webdriver/lib/by.js

diff --git a/javascript/node/selenium-webdriver/lib/by.js b/javascript/node/selenium-webdriver/lib/by.js
index 9dcad40..fcc4304 100644
--- a/javascript/node/selenium-webdriver/lib/by.js
+++ b/javascript/node/selenium-webdriver/lib/by.js
@@ -396,7 +396,7 @@
  *     strategy.
  */
 function check(locator) {
-  if (locator instanceof By || typeof locator === 'function') {
+  if (locator instanceof By || locator instanceof RelativeBy || typeof locator === 'function') {
     return locator
   }