[libc++] Remove stray CMake install step for modulemap file (#89394)

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

@@ -1076,12 +1076,6 @@ 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)
-
   # Install the generated IWYU file to the generic include dir.
   install(FILES "${LIBCXX_GENERATED_INCLUDE_DIR}/libcxx.imp"
     DESTINATION "${LIBCXX_INSTALL_INCLUDE_DIR}"