pine64-pinebook-pro: remove superfluous ap6256-firmware package

I have been running for >1 year with the upstream linux-firmware
package (i.e. just hardware.enableRedistributableFirmware = true)

https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/WHENCE#n2767

Author: tomfitzhenry

pine64/pinebook-pro/default.nix

@@ -48,9 +48,6 @@
   ];
 
   hardware.enableRedistributableFirmware = true;
-  hardware.firmware = [
-    (pkgs.callPackage ./firmware/ap6256-firmware { })
-  ];
 
   # The default powersave makes the wireless connection unusable.
   networking.networkmanager.wifi.powersave = lib.mkDefault false;