Replace oauth2client with google-auth and google-auth-oauthlib in google-calendar integration#860

PraveenNPatil07 wants to merge 2 commits intozulip:mainzulip/python-zulip-api:mainfrom

PraveenNPatil07:fix/google-calendar-integration-847PraveenNPatil07/python-zulip-api:fix/google-calendar-integration-847Copy head branch name to clipboard