chore(deps): update dependency gh-pages to v3 (open-telemetry#1165)

Author: renovate-bot

package.json

@@ -48,7 +48,7 @@
     "eslint-plugin-header": "3.0.0",
     "@typescript-eslint/eslint-plugin": "2.34.0",
     "@typescript-eslint/parser": "2.34.0",
-    "gh-pages": "2.2.0",
+    "gh-pages": "3.0.0",
     "gts": "2.0.2",
     "husky": "3.1.0",
     "lerna": "3.22.1",