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.

Written by the indexing model from the issue text.