Document the non-compatibility with the owners plugin
Document the non-compatibility with the owners plugin

This helps admins to understand what would be required to support a
migration from the owners plugin to the code-owners plugin.

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Change-Id: I2b5faa6348a06ac5e5c18b21c4b5103bab7e3220

GerritCodeReview/plugins_code-owners,GerritCodeReview/plugins_code-owners,GerritCodeReview/plugins_code-owners,GerritCodeReview/plugins_code-owners