rtl8723bs-firmware: deprecate phases

pkgs/os-specific/linux/firmware/rtl8723bs-firmware/default.nix

···
   name = "rtl8723bs-firmware-${linuxPackages.rtl8723bs.version}";
   inherit (linuxPackages.rtl8723bs) src;
 
-  phases = [ "unpackPhase" "installPhase" ];
+  dontBuild = true;
 
   installPhase = ''
     mkdir -p                "$out/lib/firmware/rtlwifi"