Update CHANGELOG for #13976

Author: anGie44

CHANGELOG.md

@@ -33,6 +33,7 @@ BUG FIXES
 * resource/aws_opsworks_stack: Suppress equivalent `custom_json` differences [GH-14886]
 * resource/aws_rds_cluster_endpoint: Increase creation timeout to 30 minutes [GH-14862]
 * resource/aws_route53_zone_association: Correctly handle zones with over 100 VPC associations [GH-14885]
+* resource/aws_workspaces_workspace: Prevent error when `workspace_properties` `running_mode` is set to `ALWAYS_ON` [GH-13976]
 
 ## 3.4.0 (August 27, 2020)