hunspellDicts.fr-any: link fr-moderne to fr_FR

Some packages like `ibus-engines.typing-booster` require the dictionary
`fr_FR.dic` to provide proper support for the french language.

Until now the hunspell package set of nixpkgs didn't provide this
dictionary. It has been recommended to use `fr-moderne` as base and link
`fr_FR.dic` from it as done by other distros such as ArchLinux.

See https://github.com/NixOS/nixpkgs/issues/46940#issuecomment-423684570

Fixes #46940