teams: Don't use root-level throw for unsupported platforms

Unsupported platforms are handled with `meta.platforms`, there's no need
to have an extra `throw` for this.

This makes the top-level attribute `teams` attribute evaluate

pkgs/applications/networking/instant-messengers/teams/default.nix

@@ -26,8 +26,8 @@ let
   };
 
   appName = "Teams.app";
-
-  darwin = stdenv.mkDerivation {
+in
+stdenv.mkDerivation {
   inherit pname meta;
   version = versions.darwin;
 
@@ -55,8 +55,4 @@ let
     makeWrapper $out/Applications/${appName}/Contents/MacOS/Teams $out/bin/teams
     runHook postInstall
   '';
-  };
-in
-if stdenv.isDarwin
-then darwin
-else throw "Teams app for Linux has been removed as it is unmaintained by upstream. (2023-09-29)"
+}