timedatectl: avoid specifically referring to NTP

systemd-timesyncd not only does NTP, but also manages clock monotonicity
using a flags file. In future, it might learn PTP support. Hence don't
expose its enablement state as "NTP" but use the more generic term
"network time synchronization". After all, for similar reasons
systemd-timesyncd is not called systemd-ntpd.

src/timedate/timedatectl.c

@@ -136,7 +136,7 @@ static void print_status_info(const StatusInfo *i) {
                 tzset();
 
         printf("       Time zone: %s (%.*s)\n"
-               "     NTP enabled: %s\n"
+               " Network Time on: %s\n"
                "NTP synchronized: %s\n"
                " RTC in local TZ: %s\n",
                strna(i->timezone), (int) sizeof(a), have_time ? a : "n/a",
@@ -331,7 +331,7 @@ static void help(void) {
                "  set-timezone ZONE        Set system time zone\n"
                "  list-timezones           Show known time zones\n"
                "  set-local-rtc BOOL       Control whether RTC is in local time\n"
-               "  set-ntp BOOL             Control whether NTP is enabled\n",
+               "  set-ntp BOOL             Control whether network time synchronization is enabled\n",
                program_invocation_short_name);
 }