Remove an extra trailing `` in Modules.rst, NFC

Author: hokein

clang/docs/Modules.rst

@@ -152,7 +152,7 @@ first include path that would refer to the current file. ``#include_next`` is
 interpreted as if the current file had been found in that path.
 If this search finds a file named by a module map, the ``#include_next``
 directive is translated into an import, just like for a ``#include``
-directive.``
+directive.
 
 Module maps
 -----------