Cleanup: remove unused interfaces for helpers

I can only guess here: maybe they were added to more clearly document the public
interface of the classes? If so, I don't think that works. Developers who are
not familiar with the convention will just add a new public method to the class
without updating the interface.

pkg/gui/controllers/helpers/working_tree_helper.go

@@ -12,13 +12,6 @@ import (
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 )
 
-type IWorkingTreeHelper interface {
-	AnyStagedFiles() bool
-	AnyTrackedFiles() bool
-	IsWorkingTreeDirty() bool
-	FileForSubmodule(submodule *models.SubmoduleConfig) *models.File
-}
-
 type WorkingTreeHelper struct {
 	c             *HelperCommon
 	refHelper     *RefsHelper