fix(chromeos): Fix loading of node-fetch library (#87)

node-fetch is an ES module, and you can't require() ESM from a non-ESM
script. I'm not sure when this changed, or with what versions of node
and this package it used to work, but downgrading to node-fetch v2 gives
us the non-ESM version that works.

Author: joeyparrish

backends/chromeos/package-lock.json

@@ -31,7 +31,7 @@
   },
   "dependencies": {
     "generic-webdriver-server": "^1.1.5",
-    "node-fetch": "^3.3.2",
+    "node-fetch": "^2.7.0",
     "node-ssh": "^13.2.0",
     "yargs": "^17.7.2"
   },