fix: upgrade proxy-agent to fix the security vulnerability. (#368)

Ref: https://app.snyk.io/vuln/SNYK-JS-PACRESOLVER-1564857

Author: hyj1991

package.json

@@ -42,7 +42,7 @@
     "humanize-ms": "^1.2.0",
     "iconv-lite": "^0.4.15",
     "ip": "^1.1.5",
-    "proxy-agent": "^4.0.1",
+    "proxy-agent": "^5.0.0",
     "pump": "^3.0.0",
     "qs": "^6.4.0",
     "statuses": "^1.3.1",