Fix sed Command Compatibility Issue in add-lang-to-versions-template-% Target on macOS

[alperozturk96]

In the add-lang-to-versions-template-% Makefile target, the following error is produced on macOS.

sed: 1: "./_templates/versions.html": invalid command code .
make[2]: *** [add-lang-to-versions-template-af] Error 1
make[1]: *** [html] Error 2
make: *** [user-manual-html] Error 2