firefox: switch back to nixpkgs source build as it has profiling information now

home/home.nix

@@ -9,8 +9,7 @@ let
   myNur = nur.repos.schmittlauch;
 
   desktopApps = [
-    # use pre-built Mozilla binary until nixpkgs build has similar performance (build profiling information)
-    firefox-bin
+    firefox
     chromium
     falkon
     thunderbird

nixos/configuration.nix

@@ -249,6 +249,7 @@ in
     gc-keep-outputs = true
     gc-keep-derivations = true
     trusted-users = spiollinux
+    experimental-features = nix-command
   '';
   # use all cores for building
   nix.buildCores = 0;