settings: drop deprecated NetworkManager.conf option "main.monitor-connection-files"

It's deprecated and off by default for a long time.

It is bad to automatically reload connection profiles. For example, ifcfg
files may consist of multiple files, there is no guarantee that we
pick up the connection when it's fully written.

Just don't do this anymore.

Users should use D-Bus API or `nmcli connection reload` or `nmcli
connection load $FILENAME` to reload profiles from disk.
12 jobs for th/drop-monitor-connection-files in 34 minutes and 42 seconds (queued for 47 seconds)
Status Job ID Name Coverage
  Test
passed #314446
allowed to fail
checkpatch

00:00:56

passed #314453
t_debian:9

00:19:25

passed #314455
t_debian:sid

00:17:15

manual #314454
allowed to fail manual
t_debian:testing
passed #314447
t_fedora:28

00:26:50

passed #314448
t_fedora:29

00:33:11

passed #314449
t_fedora:30

00:33:28

manual #314450
allowed to fail manual
t_fedora:rawhide
passed #314451
t_ubuntu:16.04

00:19:26

passed #314452
t_ubuntu:18.04

00:26:25

 
  External
passed NetworkManager test verification

passed NetworkManager test verification

05:45:12