mpvScripts.mpris: fix build

[lukebfox]

Motivation for this change

#100771

Things done

Updated derivation argument to be more in line with wrapper methodology.
Tested mpv wrapped with mpris and it builds and works.

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[doronbehar]

Thanks for the fix! Could please only change the commit message to:

mpvScripts.mpris: Use mpv-unwrapped

Needed after #88620 to fix evaluation in some cases. Fixes #100771

[SuperSandro2000]

Result of nixpkgs-review pr 100779 run on x86_64-linux 1

1 package built:

• mpvScripts.mpris