CMake config should not include a find of fmt if it's internalized (#3739)

Author: lgritz

src/cmake/Config.cmake.in

@@ -17,7 +17,7 @@ if (NOT @OPENIMAGEIO_CONFIG_DO_NOT_FIND_IMATH@ AND NOT OPENIMAGEIO_CONFIG_DO_NOT
     endif ()
 endif ()
 
-if (NOT @OIIO_USING_FMT_LOCAL@)
+if (NOT @OIIO_USING_FMT_LOCAL@ AND NOT @INTERNALIZE_FMT@)
     find_dependency(fmt)
 endif ()