[libc++] Remove stray CMake install step for modulemap file

The modulemap file is not generated anymore, so it's just part of our
list of includes and gets installed like every other header. We don't
need a special step to install it anymore. This was overlooked when I
removed the generation of the modulemap file.

Author: ldionne

libcxx/include/CMakeLists.txt

@@ -1068,12 +1068,6 @@ if (LIBCXX_INSTALL_HEADERS)
     PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
     COMPONENT cxx-headers)
 
-  # Install the generated modulemap file to the generic include dir.
-  install(FILES "${LIBCXX_GENERATED_INCLUDE_DIR}/module.modulemap"
-    DESTINATION "${LIBCXX_INSTALL_INCLUDE_DIR}"
-    PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
-    COMPONENT cxx-headers)
-
   if (NOT CMAKE_CONFIGURATION_TYPES)
     add_custom_target(install-cxx-headers
                       DEPENDS cxx-headers