Add known issue about error on branch deletion (#18858)

Author: mattpollard

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

@@ -132,6 +132,7 @@ sections:
     - A race condition can cause dependency graph database migrations to appear to fail.
     - Instances with a custom timezone that were upgraded from an earlier release of GitHub Enterprise Server may have incorrect timestamps in the web UI.
     - Old builds of Pages are not cleaned up, which could fill up the user disk (`/data/user/`).
+    - When deleting a branch after merging a pull request, an error message appears although the branch deletion succeeds.
 
   deprecations:
     - heading: Deprecation of GitHub Enterprise Server 2.19

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

@@ -44,6 +44,7 @@ sections:
     - 'Dependency graph fails to parse `yarn.lock` Javascript manifest files, resulting in HTTP 500 errors in logs.'
     - 'Instances with a custom timezone that were upgraded from an earlier release of GitHub Enterprise Server may have incorrect timestamps in the web UI.'
     - 'Old builds of Pages are not cleaned up, which could fill up the user disk (`/data/user/`).'
+    - 'When deleting a branch after merging a pull request, an error message appears although the branch deletion succeeds.'
     - |
       Users may experience assets such as avatars not loading, or a failure to push/pull code. This may be caused by a PID mismatch in the `haproxy-cluster-proxy` service. To determine if you have an affected instance:
 

data/release-notes/3-0/2.yml

@@ -30,6 +30,7 @@ sections:
     - Jupyter Notebook rendering in the web UI may fail if the notebook includes non-ASCII UTF-8 characters.
     - reStructuredText (RST) rendering in the web UI may fail and instead display raw RST markup text.
     - Old builds of Pages are not cleaned up, which could fill up the user disk (`/data/user/`).
+    - When deleting a branch after merging a pull request, an error message appears although the branch deletion succeeds.
     - |
       Users may experience assets such as avatars not loading, or a failure to push/pull code. This may be caused by a PID mismatch in the `haproxy-cluster-proxy` service. To determine if you have an affected instance:
 

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

@@ -29,6 +29,7 @@ sections:
     - Jupyter Notebook rendering in the web UI may fail if the notebook includes non-ASCII UTF-8 characters.
     - reStructuredText (RST) rendering in the web UI may fail and instead display raw RST markup text.
     - Old builds of Pages are not cleaned up, which could fill up the user disk (`/data/user/`).
+    - When deleting a branch after merging a pull request, an error message appears although the branch deletion succeeds.
     - |
       Log rotation may fail to signal services to transition to new log files, leading to older log files continuing to be used, and eventual root disk space exhaustion.
       To remedy and/or prevent this issue, run the following commands in the [administrative shell](https://docs.github.com/en/enterprise-server/admin/configuration/accessing-the-administrative-shell-ssh) (SSH), or contact [GitHub Enterprise Support](https://enterprise.githubsupport.com/hc/en-us) or [GitHub Premium Support](https://premium.githubsupport.com/) for assistance:

data/release-notes/3-0/4.yml

@@ -22,3 +22,4 @@ sections:
     - When "Users can search GitHub.com" is enabled with GitHub Connect, issues in private and internal repositories are not included in GitHub.com search results.
     - Jupyter Notebook rendering in the web UI may fail if the notebook includes non-ASCII UTF-8 characters.
     - reStructuredText (RST) rendering in the web UI may fail and instead display raw RST markup text.
+    - When deleting a branch after merging a pull request, an error message appears although the branch deletion succeeds.

data/release-notes/3-0/5.yml

@@ -23,3 +23,4 @@ sections:
     - Git LFS tracked files [uploaded through the web interface](https://github.com/blog/2105-upload-files-to-your-repositories) are incorrectly added directly to the repository.
     - Issues cannot be closed if they contain a permalink to a blob in the same repository where the file path is longer than 255 characters.
     - When "Users can search GitHub.com" is enabled with GitHub Connect, issues in private and internal repositories are not included in GitHub.com search results.
+    - When deleting a branch after merging a pull request, an error message appears although the branch deletion succeeds.