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`

首先追蹤 github-actions.remote-name 設定如何解析上游 remote，以及如何讀取其 Git 設定。使用值為 no_push 的 pushurl 重現此問題，然後驗證 repository、workflow 和 secrets 資訊仍然是從 remote 的 url 和 fetch 設定載入，而不是因為 pushurl 而遭到拒絕。

由索引模型根據 Issue 內容生成。