Keep default post visibility/privacy when replying

### Problem I have

I have a private instance of GoToSocial with default visibility set to followers only. But when I reply to a post with different visibility, Phanpy changes the privacy of the reply to match that of the post being replied to.

This also happens with my Mastodon instance.

### Solution I'd like

This is bad because my posts, which by default should only be visible to my followers, end up being visible to more people, depending on the privacy of the post being replied to.

So I'd like to suggest that Phanpy keep the default visibility when replying, unless the user explicitly and autonomously changes it.

### Alternatives considered

_No response_

### Other

Thank you.

PS.: I did a quick search in the issues page before posting this.