bazarr: use libarchive instead of unar

unar is ObjC, doesn't build currently and is largely dead.
Bazarr only uses it to unpack RAR archives, so just give it
libarchive bsdtar instead, which can handle any reasonable archive,
is not unfree and is not dead.

pkgs/servers/bazarr/default.nix

@@ -1,9 +1,9 @@
-{ stdenv, lib, fetchurl, makeWrapper, unzip, python3, unar, ffmpeg, nixosTests }:
+{ stdenv, lib, fetchurl, makeWrapper, unzip, python3, libarchive, ffmpeg, nixosTests }:
 
 let
   runtimeProgDeps = [
     ffmpeg
-    unar
+    libarchive
   ];
 in
 stdenv.mkDerivation rec {