Remove another unnecessary refresh

This was added after this PR comment:
#3276 (comment)

> Can we do a refresh after this reset so that the screen shows that the patch
> has been cancelled? That way, if we cancel on the next popup, the screen will
> be in a valid state.

I don't understand what "cancel on the next popup" means; there is no further
popup after this code.

Author: stefanhaller

pkg/gui/controllers/commits_files_controller.go

@@ -313,9 +313,6 @@ func (self *CommitFilesController) discard(selectedNodes []*filetree.CommitFileN
 				// Reset the current patch if there is one.
 				if self.c.Git().Patch.PatchBuilder.Active() {
 					self.c.Git().Patch.PatchBuilder.Reset()
-					if err := self.c.Refresh(types.RefreshOptions{Mode: types.BLOCK_UI}); err != nil {
-						return err
-					}
 				}
 
 				for _, node := range selectedNodes {