Modernize context import in internal/fuse

Migrated using `go fix`.

internal/fuse/other.go

@@ -3,9 +3,10 @@
 package fuse
 
 import (
+	"context"
+
 	"bazil.org/fuse"
 	"github.com/restic/restic/internal/restic"
-	"golang.org/x/net/context"
 )
 
 type other struct {