Update dependency @grpc/proto-loader to ^0.4.0

Author: renovate-bot

packages/opencensus-exporter-ocagent/package-lock.json

@@ -63,7 +63,7 @@
     "typescript": "~3.2.0"
   },
   "dependencies": {
-    "@grpc/proto-loader": "^0.3.0",
+    "@grpc/proto-loader": "^0.4.0",
     "@opencensus/core": "^0.0.8",
     "@opencensus/nodejs": "^0.0.8",
     "google-proto-files": "^0.18.0",