Update known issues for 3.0.1 - lfs/deploy keys (#18161)

Author: chiph

data/release-notes/3-0/1.yml

@@ -35,3 +35,4 @@ sections:
     - 'When maintenance mode is enabled, some services continue to be listed as "active processes". The services identified are expected to run during maintenance mode. If you experience this issue and are unsure, contact [GitHub Enterprise Support](https://enterprise.githubsupport.com/hc/en-us) or [GitHub Premium Support](https://premium.githubsupport.com/).'
     - 'Duplicated logging to `/var/log/messages`, `/var/log/syslog`, and `/var/log/user.log` results in increased root volume utilization.'
     - 'Users can dismiss a mandatory message without checking all checkboxes.'
+    - 'Repository [deploy keys](/developers/overview/managing-deploy-keys) are unable to be used with repositories containing LFS objects.'