fusefrontend: drop unused haveGetdents warning

We don't actually print that warning anymore.

internal/fusefrontend/fs_dir.go

@@ -8,7 +8,6 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
-	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
@@ -257,9 +256,6 @@ retry:
 	return fuse.OK
 }
 
-// If syscallcompat.HaveGetdents is false we will warn once about it
-var haveGetdentsWarnOnce sync.Once
-
 // OpenDir implements pathfs.FileSystem
 func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
 	tlog.Debug.Printf("OpenDir(%s)", dirName)