added changelog entry

CHANGELOG.md

@@ -3,6 +3,7 @@
 This is a list of high-level changes for each release of AWX. A full list of commits can be found at `https://github.com/ansible/awx/releases/tag/<version>`.
 
 ## 12.0.0 (TBD)
+- Removed memcached as a dependency of AWX (https://github.com/ansible/awx/pull/7240) 
 - Moved to a single container image build instead of separate awx_web and awx_task images. The container image is just `awx` (https://github.com/ansible/awx/pull/7228)
 - Official AWX container image builds now use a two-stage container build process that notably reduces the size of our published images (https://github.com/ansible/awx/pull/7017)
 - Removed support for HipChat notifications ([EoL announcement](https://www.atlassian.com/partnerships/slack/faq#faq-98b17ca3-247f-423b-9a78-70a91681eff0)); all previously-created HipChat notification templates will be deleted due to this removal.
@@ -19,6 +20,7 @@ This is a list of high-level changes for each release of AWX. A full list of com
 - Fixed a bug that broke external log aggregation support for URL paths that include the = character (such as the tokens for SumoLogic) (https://github.com/ansible/awx/issues/7139)
 - Fixed a bug that prevented organization admins from removing labels from workflow job templates (https://github.com/ansible/awx/pull/7143)
 
+
 ## 11.2.0 (Apr 29, 2020)
 
 - Inventory updates now use collection-based plugins by default (in Ansible 2.9+):