Revert "Write files in O_SYNC for fs backend to protect against machine crashes (#9434)"

This reverts commit 4843affd0e.

cmd/fs-v1-helpers.go

@@ -321,7 +321,7 @@ func fsCreateFile(ctx context.Context, filePath string, reader io.Reader, buf []
 		return 0, err
 	}
 
-	writer, err := lock.Open(filePath, os.O_CREATE|os.O_WRONLY|os.O_SYNC, 0666)
+	writer, err := lock.Open(filePath, os.O_CREATE|os.O_WRONLY, 0666)
 	if err != nil {
 		return 0, osErrToFSFileErr(err)
 	}