Clarify replication of refs/meta/config when refspec is 'all refs'

Update the documentation to mention that the `refs/meta/config`
branch will not be replicated when the push refspec is 'all refs',
but the `replicatePermissions` option is disabled for the remote.

Change-Id: I6932b5230bc118543a218a312c7f06c095b44a56
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index d9662d9..0737a94 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -130,6 +130,10 @@
 
 	Defaults to `+refs/*:refs/*` (all refs) if not specified.
 
+	Note that the `refs/meta/config` branch is only replicated
+	when `replicatePermissions` is true, even if the push refspec
+	is 'all refs'.
+
 [2]: #example_file
 
 remote.NAME.timeout