Update README.md

Drop the broken community link.
We're using GitHub's "discussions" feature now, instead.

Closes #334

Author: lovelydinosaur

README.md

@@ -19,8 +19,6 @@ Databases is suitable for integrating against any async Web framework, such as [
 
 **Documentation**: [https://www.encode.io/databases/](https://www.encode.io/databases/)
 
-**Community**: [https://discuss.encode.io/c/databases](https://discuss.encode.io/c/databases)
-
 **Requirements**: Python 3.6+
 
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