A mod that disables the The world folder contains symbolic links warning.

Upon startup, this mod just writes [regex].* to .minecraft/allowed_symlinks.txt, which disables the warning.

Windows

Windows uses shortcuts, which are not symlinks and are not supported by Minecraft.

Removing

Removing the mod will not remove the allowed_symlinks.txt file, you have to manually delete that file after removing the mod if you would like to see the warning again for whatever reason.