fix(deps): update dependency merge-stream to v2 (#624)

Author: renovate[bot]

package.json

@@ -67,7 +67,7 @@
     "google-gax": "^0.26.0",
     "is": "^3.2.1",
     "lodash.snakecase": "^4.1.1",
-    "merge-stream": "^1.0.1",
+    "merge-stream": "^2.0.0",
     "p-queue": "^5.0.0",
     "protobufjs": "^6.8.6",
     "split-array-stream": "^2.0.0",