docs: add changlog entry for v4.12.1

Author: Jeremy Udit

CHANGELOG.md

@@ -1,3 +1,12 @@
+## 4.12.1 (Jun 30, 2021)
+
+BUG FIXES:
+
+- Fix URL construction when authenticating via GitHub App for enterprise ([#835](https://github.com/integrations/terraform-provider-github/issues/835))
+- Create internal repositories without update sequence for `github_repository` ([#794](https://github.com/integrations/terraform-provider-github/issues/794))
+- Set `name` and `full_name` attributes as computed for `github_repository` data source ([#780](https://github.com/integrations/terraform-provider-github/issues/780))
+- Allow empty array for `selected_repository_ids` attribute of `github_actions_organization_secret` resource ([#843](https://github.com/integrations/terraform-provider-github/issues/843))
+
 ## 4.12.0 (Jun 18, 2021)
 
 ENHANCEMENTS: