Setting upstream pushurl to a bad value to prevent pushing prevents branch from being used to find Actions info

**Describe the bug**

If `pushurl` has been set to prevent a remote from being pushable (which I tend to do in order to ensure I never ever push upstream, https://stackoverflow.com/a/10260389), then the extension is unable to find any info about the repo, workflows, secrets, etc.

**To Reproduce**
Steps to reproduce the behavior:
1. Check out a fork.
1. Add an upstream.
1. Set `upstream` to be unpushable using (`git remote set-url --push upstream no_push`)
1. Set `"github-actions.remote-name": "upstream"` in `settings.json`.

**Expected behavior**

The repo works as normal. After all, all of the other settings point to the right places:

```ini
[remote "upstream"]
url = git@github.com:microsoft/TypeScript.git
fetch = +refs/heads/*:refs/remotes/upstream/*
gh-resolved = base
pushurl = no_push
```

**Screenshots**

With pushurl set:



With it unset:



**Extension Version**
`v0.26.2`

Start by tracing how the github-actions.remote-name setting resolves the upstream remote and how its Git configuration is read. Reproduce the issue with a pushurl of no_push, then verify that repository, workflow, and secrets information still loads from the remote's url and fetch configuration rather than being rejected because of pushurl.

Rédigé par le modèle d'indexation à partir du texte de l'issue.