path-util: fix typo in comment

The comment makes a reference to the function fchmod_path() but this
function does not exist in the source tree.

However, the function fchmod_opath() exists; it was introduced by the
commit 4dfaa528d4.

As the comment tells, the function futimens_opath() introduced by the
commit f25bff5eaf is similar to the
function fchmod_opath(); therefore, it should reference it.

This fixes the typo in the comment by referencing the proper function
fchmod_opath().

src/basic/fs-util.c

@@ -304,7 +304,7 @@ int fchmod_opath(int fd, mode_t m) {
 }
 
 int futimens_opath(int fd, const struct timespec ts[2]) {
-        /* Similar to fchmod_path() but for futimens() */
+        /* Similar to fchmod_opath() but for futimens() */
 
         if (utimensat(AT_FDCWD, FORMAT_PROC_FD_PATH(fd), ts, 0) < 0) {
                 if (errno != ENOENT)