chore(deps): update dependency geventhttpclient to v2 (GoogleCloudPlatform#1013)

Author: renovate-bot

src/loadgenerator/requirements.txt

@@ -29,7 +29,7 @@ gevent==21.12.0
     # via
     #   geventhttpclient
     #   locust
-geventhttpclient==1.5.5
+geventhttpclient==2.0.2
     # via locust
 greenlet==1.1.3
     # via gevent