chore: update DEN meetup to reflect new name + URL (graphql#758)

Author: grxy

site/community/Community-Events.md

@@ -41,7 +41,7 @@ GraphQL conference organized by Apollo.
 - [GraphQL Columbus](https://www.meetup.com/GraphQL-Columbus/)
 - [GraphQL Vancouver](https://www.meetup.com/GraphQL-Vancouver/)
 - [GraphQL Minneapolis](https://www.meetup.com/GraphQL-MN/)
-- [GraphQL Denver/Boulder](https://www.meetup.com/GraphQL-Denver-Boulder-Meetup/)
+- [GraphQL Denver](https://www.meetup.com/graphql-denver)
 - [GraphQL By the Bay (San Francisco)](https://www.meetup.com/graphql-by-the-bay/)
 
 ### South America