chore(deps): update dependency gaxios to v4

Author: renovate-bot

datastore/functions/package.json

@@ -20,7 +20,7 @@
   "devDependencies": {
     "@google-cloud/functions-framework": "^1.1.1",
     "child-process-promise": "^2.2.1",
-    "gaxios": "^3.0.0",
+    "gaxios": "^4.0.0",
     "mocha": "^8.0.0",
     "proxyquire": "^2.1.0",
     "sinon": "^9.0.0",