Fix docs build

This amends 7e2411c

Author: AaronBallman

clang/docs/StandardCPlusPlusModules.rst

@@ -29,8 +29,8 @@ In order to better understand the compiler's behavior, it is helpful to
 understand some terms and definitions for readers who are not familiar with the
 C++ feature. This document is not a tutorial on C++; it only introduces
 necessary concepts to better understand use of modules in a project. Other
-resources at `Wikipedia<https://en.wikipedia.org/wiki/Modules_(C++)>`_ and
-`cppreference<https://en.cppreference.com/w/cpp/language/modules.html>`_ can
+resources at `Wikipedia <https://en.wikipedia.org/wiki/Modules_(C++)>`_ and
+`cppreference <https://en.cppreference.com/w/cpp/language/modules.html>`_ can
 provide more background information about modules if needed.
 
 Background and terminology