chore(deps): update dependency @types/mongodb to v4

Author: renovate[bot]

packages/opencensus-instrumentation-mongodb/package-lock.json

@@ -51,7 +51,7 @@
   "devDependencies": {
     "@types/bson": "1.0.11",
     "@types/mocha": "8.2.3",
-    "@types/mongodb": "3.0.19",
+    "@types/mongodb": "4.0.6",
     "@types/node": "10.17.60",
     "@types/shimmer": "1.0.2",
     "codecov": "3.8.3",