docs(changelog): explicitly list the tf versions <1.x removal in the CHANGELOG.md (#2780)

* docs(changelog): explicitly list the tf versions <1.x removal in the CHANGELOG.md

* Apply suggestions from code review

Co-authored-by: nitrocode <[email protected]>

Author: NitriKx

CHANGELOG.md

@@ -6,6 +6,9 @@ Bugfixes and new Features
 
 https://github.com/runatlantis/atlantis/releases/tag/v0.21.0
 
+## Breaking changes
+* Terraform version 1.x have been removed to deprecate beta versions of terraform and reduce the docker image size. Each version of terraform is about 80 MB. ([#2619](https://github.com/runatlantis/atlantis/pull/2619))
+
 # v0.20.1
 
 Bugfixes and new Features