Update CHANGELOG.md

Author: armsnyder

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 2.12.0 (Unreleased)
 
+NOTES:
+* If you are using the `environment_scope` attribute of `gitlab_project_variable` to manage multiple variables with the same key, it is recommended to use GitLab 13.4+. See [this related GitLab issue](https://gitlab.com/gitlab-org/gitlab/-/issues/9912) for older versions.
+
 FEATURES:
 * **New Data Source:** `gitlab_group_membership` [GH-264]
 * **New Resource:** `gitlab_project_level_mr_approvals` [GH-356]
@@ -15,13 +18,16 @@ ENHANCEMENTS:
 * resource/gitlab_project: New `import_url` attribute [GH-381]
 * resource/gitlab_project_push_rules: Can now be imported [GH-360]
 * resource/gitlab_project_variable: Better error message when a masked variable fails validation [GH-371]
+* resource/gitlab_project_variable: Automatically detect removal [GH-409]
 * resource/gitlab_service_jira: Automatically detect removal [GH-337]
 * resource/gitlab_user: The `email` attribute can be changed without forcing recreation [GH-261]
 * resource/gitlab_user: Require either the `password` or `reset_password` attribute to be set [GH-262]
 
 BUG FIXES:
 * resource/gitlab_pipeline_schedule: Fix a rare error during deletion [GH-364]
 * resource/gitlab_pipeline_schedule_variable: Fix a rare error during deletion [GH-364]
+* resource/gitlab_project_variable: Fix inconsistent reads for variables with non-unique keys [GH-409]
+* resource/gitlab_project_variable: Change the default `environment_scope` from `0` to `*` [GH-409]
 * resource/gitlab_service_jira: Fix a rare state inconsistency problem during creation [GH-363]
 * resource/gitlab_user: Fix some attributes saving incorrectly in state [GH-261]