chore: add missing semver type dependency (open-telemetry#702)

Author: dyladan

packages/opentelemetry-plugin-dns/package.json

@@ -45,6 +45,7 @@
     "@opentelemetry/tracing": "^0.3.2",
     "@types/mocha": "^5.2.7",
     "@types/node": "^12.7.12",
+    "@types/semver": "^6.2.0",
     "@types/shimmer": "^1.0.1",
     "@types/sinon": "^7.5.0",
     "codecov": "^3.6.1",