Document that changing allowedEmails may cause issues in code owner configs

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Id88e30f2b4a06164db6b6803a01a61cb769dd6d6
diff --git a/resources/Documentation/validation.md b/resources/Documentation/validation.md
index 756edd5..3b0dc95 100644
--- a/resources/Documentation/validation.md
+++ b/resources/Documentation/validation.md
@@ -62,8 +62,9 @@
   (e.g. the [accounts.visibility](../../../Documentation/config-gerrit.html#accounts.visibility)
   setting is changed, [another code owners backend is
   configured](setup-guide.html#configureCodeOwnersBackend) which now uses a
-  different syntax or different names for code owner config files, or the [file
-  extension for code owner config file is set/changed](config.html#codeOwnersFileExtension))
+  different syntax or different names for code owner config files, the [file
+  extension for code owner config file is set/changed](config.html#codeOwnersFileExtension),
+  or the [allowed email domains are changed](config.html#pluginCodeOwnersAllowedEmailDomain))
 * emails of users may change so that emails in code owner configs can no longer
   be resolved
 * imported code owner config files may get deleted or renamed so that import