chore(package): update fetch-mock to version 9.3.1

Author: greenkeeper[bot]

package.json

@@ -50,7 +50,7 @@
     "@types/node": "^13.1.0",
     "@types/node-fetch": "^2.3.3",
     "@types/once": "^1.4.0",
-    "fetch-mock": "^9.0.0",
+    "fetch-mock": "^9.3.1",
     "jest": "^24.7.1",
     "lolex": "^6.0.0",
     "prettier": "^2.0.1",