build: pin ChromeDriver version (#20940)

Since our version of Chromium is also pinned, a new ChromeDriver (that
drops support for our Chromium version) can cause random (and unrelated
to the corresponding changes) errors on CI.
This commit pins the version of ChromeDriver and it should now be
manually upgraded to a vrsion that is compatible with th currently used
Chromium version.

PR Close #20940

packages/platform-server/integrationtest/package.json

@@ -33,7 +33,7 @@
     "webpack": "^2.2.1"
   },
   "scripts": {
-    "postinstall": "webdriver-manager update --gecko false",
+    "postinstall": "webdriver-manager update --gecko false --standalone false $CHROMEDRIVER_VERSION_ARG",
     "build": "./build.sh",
     "test": "npm run build && concurrently \"npm run serve\" \"npm run protractor\" --kill-others --success first",
     "serve": "node built/server-bundle.js",