Move neutron meetings to the openstack-neutron channel

This patch proposed to move Neutron meetings from the
dedicated meeting channels to the openstack-neutron channel.
This was discussed on the Neutron team meeting at [1]

[1] https://meetings.opendev.org/meetings/networking/2021/networking.2021-06-01-14.01.log.html#l-34

Change-Id: I5d55d9335edc4a88657257ff9ff280444d79e512

meetings/neutron-ci.yaml

@@ -4,7 +4,7 @@ agenda_url: https://etherpad.openstack.org/p/neutron-ci-meetings
 schedule:
   - time:       '1500'
     day:        Tuesday
-    irc:        openstack-meeting-3
+    irc:        openstack-neutron
     frequency:  weekly
     start_date: 20170131
 chair: Slawek Kaplonski (slaweq), Rodolfo Alonso (ralonsoh)

meetings/neutron-drivers-meeting.yaml

@@ -4,7 +4,7 @@ agenda_url: https://wiki.openstack.org/wiki/Meetings/NeutronDrivers
 schedule:
   - time:       '1400'
     day:        Friday
-    irc:        openstack-meeting
+    irc:        openstack-neutron
     frequency:  weekly
     start_date: 20180406
 chair:  Slawek Kaplonski (slaweq), Miguel Lavalle (mlavalle)

meetings/neutron-l3-sub-team-meeting.yaml

@@ -4,7 +4,7 @@ agenda_url: https://etherpad.openstack.org/p/neutron-l3-subteam
 schedule:
   - time:       '1400'
     day:        Wednesday
-    irc:        openstack-meeting
+    irc:        openstack-neutron
     frequency:  biweekly-odd
     start_date: 20200720
 chair:  Liu Yulong (liuyulong), Brian Haley (haleyb)

meetings/neutron-team-meeting.yaml

@@ -4,7 +4,7 @@ agenda_url: https://wiki.openstack.org/wiki/Network/Meetings
 schedule:
   - time:       '1400'
     day:        Tuesday
-    irc:        openstack-meeting-3
+    irc:        openstack-neutron
     frequency:  weekly
     start_date: 20160202
 chair:  Slawek Kaplonski (slaweq), Miguel Lavalle (mlavalle)