tabby: mark broken

It's been broken for months for both platforms. Presumably a bump to
0.32 could fix it: https://github.com/NixOS/nixpkgs/pull/485360 but it's
also broken with our rust version and requires an upstream fix first.

(cherry picked from commit 48d4cf12ba)

pkgs/by-name/ta/tabby/package.nix

@@ -188,6 +188,6 @@ rustPlatform.buildRustPackage {
     mainProgram = "tabby";
     license = lib.licenses.asl20;
     maintainers = [ lib.maintainers.ghthor ];
-    broken = stdenv.hostPlatform.isDarwin && !stdenv.hostPlatform.isAarch64;
+    broken = true;
   };
 }