chore: pin @fastify/busboy to a version that supports node 12 (#1130)

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Fixes #1129 🦕

Author: mctavish

package.json

@@ -45,6 +45,7 @@
   },
   "dependencies": {
     "@google-cloud/common": "^4.0.0",
+    "@fastify/busboy": "1.1.0",
     "acorn": "^8.0.0",
     "coffeescript": "^2.0.0",
     "console-log-level": "^1.4.0",
@@ -57,6 +58,11 @@
     "source-map": "^0.8.0-beta.0",
     "split": "^1.0.0"
   },
+  "overrides": {
+    "firebase-admin": {
+      "@fastify/busboy": "1.1.0"
+    }
+  },
   "devDependencies": {
     "@compodoc/compodoc": "1.1.19",
     "@types/acorn": "^4.0.2",