Pin `tough-cookie` to version `4.0.0` to prevent being updated by npm audit fix.

`npm audit fix` will update `touch-cookie` to version `4.1.3` which seems to be a breaking update for our usage.

GitOrigin-RevId: 2a583b3673573984b425a98ee94c95ff4db27124

services/web/package.json

@@ -243,7 +243,7 @@
     "rimraf": "2.2.6",
     "sanitize-html": "^2.8.1",
     "scroll-into-view-if-needed": "^2.2.25",
-    "tough-cookie": "^4.0.0",
+    "tough-cookie": "4.0.0",
     "tsscmp": "^1.0.6",
     "underscore": "^1.13.1",
     "utf-8-validate": "^5.0.2",