Handle different push and fetch remotes
My repo can be fetched from `https://git.sprovoost.nl/instablossom.git/` by anyone. To push I use a git:// remote which goes over SSH.
But in order to use git-remote-nostr I had to replace both remotes with:
```
origin nostr://npub1s6z7hmmx2vud66f3utxd70qem8cwtggx0jgc7gh8pqwz2k8cltuqrdwk4c/instablossom
```
This causes a problem, because git push will now update the repo on Nostr but then it fails trying to push to the https origin. I can work around this by adding a second origin and manually pushing there.
I ideally I should be able to configure the push origin that git-remote-nostr uses under the hood. That URL should not be published (it's unreachable).