mobilizon: drop unnecessary cmake dependency

fast_html already defines this in override.
mix hook changes allowed cmake hook changes to run, which fail because it's unneeded.

pkgs/by-name/mo/mobilizon/package.nix

@@ -28,7 +28,6 @@ beamPackages.mixRelease rec {
 
   nativeBuildInputs = [
     git
-    cmake
   ];
 
   mixNixDeps = import ./mix.nix {