tdesktop: 1.9.4 -> 1.9.7 (#78390)

This also properly enables the spell checking with enchant2.

Note: This requires a proper configuration.
A quick and dirty solution (not recommended) could look like this:
install -Dt ~/.config/enchant/hunspell/ $(nix-build -A hunspellDicts.en_US)/share/hunspell/en_US.{aff,dic}