octavePackages.windows: Remove broken, add meta.platforms

The package is not broken on Linux/Darwin, those platforms don't have
COM interfaces. During Octave's "pkg install", it checks for this fact
and will error if they are not available, see below.

```
error: __COM__: Your system doesn't support the COM interface
```

pkgs/development/octave-modules/windows/default.nix

@@ -43,6 +43,6 @@ buildOctavePackage rec {
     license = lib.licenses.gpl3Plus;
     maintainers = with lib.maintainers; [ KarlJoad ];
     description = "Provides COM interface and additional functionality on Windows";
-    broken = true;
+    platforms = lib.platforms.windows;
   };
 }