Reword CFG_ETC_HIDE_BLACKLISTED explanation

To make it clearer.

Added on commit ded5020 ("opt-in: skip blacklisted files in
private-etc - netblue30#5010, netblue30#5230", 2023-01-15) / PR netblue30#5591.

src/firejail/fs_etc.c

@@ -265,8 +265,9 @@ void fs_private_dir_list(const char *private_dir, const char *private_run_dir, c
 void fs_rebuild_etc(void) {
  int have_dhcp = 1;
  if (cfg.dns1 == NULL && !any_dhcp()) {
- // this function has the effect that updates to files using rename(2) don't propagate into the sandbox
- // avoid this in the default setting, in order to not break /etc/resolv.conf (issue #5010)
+ // Disabling this option ensures that updates to files using
+ // rename(2) propagate into the sandbox, in order to avoid
+ // breaking /etc/resolv.conf (issue #5010).
  if (!checkcfg(CFG_ETC_HIDE_BLACKLISTED))
  return;
  have_dhcp = 0;