DOCS: fix broken link in src/doc/roles.md

src/doc/roles.md

@@ -10,7 +10,7 @@ users may have the same role, and there may be roles without any users.
 
 The user and their roles are always returned by the server in answers to requests
 and can thus be interpreted and used by clients.  The most important use though
-is [permission](permissions.rst) checking in the server: Access and
+is [permission](permissions) checking in the server: Access and
 modification of
 entities can be controlled via roles, so that users of a given role are allowed
 or denied certain actions.  Incidentally, the permission to edit the permissions
@@ -32,4 +32,4 @@ There are some special roles, which are automatically assigned to users:
 
 Except for the `anonymous` role, these special roles are not returned by the
 server, but can nevertheless be used to define
-[permissions](permissions.rst).
+[permissions](permissions).