treewide: go: inherit platforms instead of using platforms.all

`buildGoModule` and `buildGoPackage` by default inherit the `platforms`
from go. That seems better than explicitly configuring `platforms.all`.

There are also many packages that specify 'linux + darwin' - this is
even suggested in the documentation. We might also want to update those,
but let's do the noncontroversial change first.

pkgs/applications/networking/cluster/helm/plugins/helm-diff.nix

@@ -30,6 +30,5 @@ buildGoModule rec {
     inherit (src.meta) homepage;
     license = licenses.apsl20;
     maintainers = with maintainers; [ yurrriq ];
-    platforms = platforms.all;
   };
 }