`.github/workflows/code-coverage.yml` needs `permissions: contents: write`

Due to

https://www.stepsecurity.io/blog/hackerbot-claw-github-actions-exploitation

we'll be changing the default GHA permissions for boostorg to read-only.

Since `.github/workflows/code-coverage.yml` does `git push`, it will need to be updated to contain

```
permissions:
contents:
write
```
(https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#permissions)

I'd also recommend enabling branch protection, so that the `master` and `develop` branches can't be rewritten or deleted.

Open .github/workflows/code-coverage.yml and review the workflow's existing git push step alongside GitHub's permissions syntax documentation. Add the requested contents write permission, then verify that the workflow retains the permission needed for its push; branch protection for master and develop is also recommended in the issue.

Written by the indexing model from the issue text.