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/files_helper.go

@@ -6,12 +6,6 @@ import (
 	"github.com/samber/lo"
 )
 
-type IFilesHelper interface {
-	EditFiles(filenames []string) error
-	EditFileAtLine(filename string, lineNumber int) error
-	OpenFile(filename string) error
-}
-
 type FilesHelper struct {
 	c *HelperCommon
 }
@@ -22,8 +16,6 @@ func NewFilesHelper(c *HelperCommon) *FilesHelper {
 	}
 }
 
-var _ IFilesHelper = &FilesHelper{}
-
 func (self *FilesHelper) EditFiles(filenames []string) error {
 	absPaths := lo.Map(filenames, func(filename string, _ int) string {
 		absPath, err := filepath.Abs(filename)