ci: codecov: use `--retry-connrefused` with curl
ci: codecov: use `--retry-connrefused` with curl

While it might not help with the following, it certainly might happen as
well.

```
+ curl -S -L --connect-timeout 5 --retry 6 -s https://codecov.io/bash -o codecov-upload.sh
curl: (16) Error in the HTTP2 framing layer
```

nicoddemus/pytest,The-Compiler/pytest,The-Compiler/pytest,alfredodeza/pytest,Akasurde/pytest,markshao/pytest,nicoddemus/pytest,RonnyPfannschmidt/pytest,pytest-dev/pytest