Update CHANGELOG.md (#461)

Author: leofigy

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## [v0.9.1](https://github.com/mongodb/terraform-provider-mongodbatlas/tree/v0.9.1) (2021-05-17)
+[Full Changelog](https://github.com/mongodb/terraform-provider-mongodbatlas/compare/v0.9.0...v0.9.1)
+
+No content change, same as pre-release
+
 ## [v0.9.1-pre.1](https://github.com/mongodb/terraform-provider-mongodbatlas/tree/v0.9.1-pre.1) (2021-05-14)
 [Full Changelog](https://github.com/mongodb/terraform-provider-mongodbatlas/compare/v0.9.0...v0.9.1-pre.1)