internal/lockedfile: keep objects alive while stopping cleanups

Fixes https://go.dev/issues/74780.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/lockedfile/internal/filelock/filelock.go

@@ -8,7 +8,6 @@
 package filelock
 
 import (
-	"errors"
 	"io/fs"
 )
 
@@ -74,10 +73,3 @@ func (lt lockType) String() string {
 		return "Unlock"
 	}
 }
-
-// IsNotSupported returns a boolean indicating whether the error is known to
-// report that a function is not supported (possibly for a specific input).
-// It is satisfied by errors.ErrUnsupported as well as some syscall errors.
-func IsNotSupported(err error) bool {
-	return errors.Is(err, errors.ErrUnsupported)
-}