juju#13525

Update the juju/replicaset/v2 dependency to fix an issue updating the mongo replicaset where node addresses change.

Supersedes juju#13521 

## QA steps

```
# Setup lxd instances and push required keys
$ lxc launch ubuntu:18.04 t1
$ lxc launch ubuntu:18.04 t2
$ lxc launch ubuntu:18.04 t3
$ lxc file push --uid 0 --gid 0 --mode 644 ~/.local/share/juju/ssh/juju_id_rsa.pub t1/root/.ssh/authorized_keys
$ lxc file push --uid 0 --gid 0 --mode 644 ~/.local/share/juju/ssh/juju_id_rsa.pub t2/root/.ssh/authorized_keys
$ lxc file push --uid 0 --gid 0 --mode 644 ~/.local/share/juju/ssh/juju_id_rsa.pub t3/root/.ssh/authorized_keys

# Add manual cloud with the address of `t1` (lxc list t1)
$ juju add-cloud manual-test --client
Cloud Types
 lxd
 maas
 manual
 openstack
 vsphere

Select cloud type: manual

Enter the ssh connection string for controller, username@<hostname or IP> or <hostname or IP>: root@$T1_IP_ADDRESS

Cloud "manual-test" successfully added to your local client.

# Bootstrap cloud with FAN support
FAN_UNDERLAY=`ip addr show dev lxdbr0 | grep /24 | awk '{print $2}' | sed 's/1/24/0/24/'`
FAN_OVERLAY='252.0.0.0/16'

$ juju bootstrap manual-test manual-test --model-default container-networking-method=fan --model-default fan-config=${FAN_UNDERLAY}=${FAN_OVERLAY}

$ juju switch controller

$ lxc list | grep RUNNING
$ juju add-machine ssh:root@$T2_IP_ADDRESS
$ juju add-machine ssh:root@$T3_IP_ADDRESS

$ juju enable-ha --to 1,2
$ juju show-controller
# check "ha-enabled" sections

# Also connect to mongo and check 'rs.status()' output
```
## Bug reference

https://bugs.launchpad.net/juju/+bug/1951813