Using "--dns" only modifies `/etc/resolv.conf` on first time start (instance creation) - not modified afterwards

### Description

I noticed that if the initial colima instance is created with `--dns 8.8.8.8 --dns 8.8.4.4` or similar those entries are written into the `/etc/resolv.conf` file.

However, that file does not seem to change afterwards if `--dns` is supplied, so colima keeps using the initially provided DNS servers - without manual changes.

checked with `colima ssh -- cat /etc/resolv.conf`

using vm type `vz` with virtiofs.

Not 100% sure if this is the intended behavior. or if the file should not change at all etc.

### Version

Colima Version: 0.5.4
Lima Version: 0.15.0
Qemu Version: 7.2.0

### Operating System

- [X] macOS Intel >= 13 (Ventura)