`migrate-repo` command retries 5 times if target repository exists

## Description

When calling the `migrate-repo` command it is checked if the target repository already exists. If the repository is found then the check method retries the call 5 time before throwing a exception. This is the call stack:

https://github.com/github/gh-gei/blob/b380004c8ab8bd1e2a4bec9c9aafedd42c9f7026/src/Octoshift/Services/GithubApi.cs#L170-L186

https://github.com/github/gh-gei/blob/b380004c8ab8bd1e2a4bec9c9aafedd42c9f7026/src/Octoshift/Services/GithubClient.cs#L48

The `GetNonSuccessAsync()` function calls a `GetWithRetry()` by passing an expected `HttpStatusCode`.

IMO the `GetNonSuccessAsync()` function should call a sub-function **without** retry and should fail if the expected `HttpStatusCode` is returned, or is this behavior intentional?

## Reproduction Steps

Run a migration against an existing repository.