signal-desktop: revert "Allow overriding the spell checker language (#44456)"

This reverts commit 9ef1406a99.

Signal Desktop removed this functionality when changing spell checkers:

  - signalapp/Signal-Desktop@6a517e4ef9
  - signalapp/Signal-Desktop@4a8f5db0a4

pkgs/applications/networking/instant-messengers/signal-desktop/default.nix

@@ -5,24 +5,9 @@
 , cups, expat, libuuid, at-spi2-core, libappindicator-gtk3, mesa
 # Runtime dependencies:
 , systemd, libnotify, libdbusmenu, libpulseaudio, xdg-utils
-# Unfortunately this also overwrites the UI language (not just the spell
-# checking language!):
-, hunspellDicts, spellcheckerLanguage ? null # E.g. "de_DE"
-# For a full list of available languages:
-# $ cat pkgs/development/libraries/hunspell/dictionaries.nix | grep "dictFileName =" | awk '{ print $3 }'
 }:
 
-let
-  customLanguageWrapperArgs = (with lib;
-    let
-      # E.g. "de_DE" -> "de-de" (spellcheckerLanguage -> hunspellDict)
-      spellLangComponents = splitString "_" spellcheckerLanguage;
-      hunspellDict = elemAt spellLangComponents 0 + "-" + toLower (elemAt spellLangComponents 1);
-    in lib.optionalString (spellcheckerLanguage != null) ''
-      --set HUNSPELL_DICTIONARIES "${hunspellDicts.${hunspellDict}}/share/hunspell" \
-      --set LC_MESSAGES "${spellcheckerLanguage}"'');
-
-in stdenv.mkDerivation rec {
+stdenv.mkDerivation rec {
   pname = "signal-desktop";
   version = "5.47.0"; # Please backport all updates to the stable channel.
   # All releases have a limited lifetime and "expire" 90 days after the release.
@@ -122,7 +107,6 @@ in stdenv.mkDerivation rec {
   preFixup = ''
     gappsWrapperArgs+=(
       --prefix LD_LIBRARY_PATH : "${lib.makeLibraryPath [ stdenv.cc.cc ] }"
-      ${customLanguageWrapperArgs}
       --add-flags "\''${NIXOS_OZONE_WL:+\''${WAYLAND_DISPLAY:+--enable-features=UseOzonePlatform --ozone-platform=wayland}}"
       --suffix PATH : ${lib.makeBinPath [ xdg-utils ]}
     )