[BUG]: Fix ActionsSelfHostedRunnersClient Delete calls

[lineville]

What happened?

Calling ActionsSelfHostedRunnersClient.DeleteEnterpriseRunner, ActionsSelfHostedRunnersClient.DeleteOrganizationRunner, ActionsSelfHostedRunnersClient.DeleteRepositoryRunner throw exceptions with the following message: The value cannot be null or empty. (Parameter 'mediaType').

The source of this error is that ApiOptions are being passed in to the delete methods which don't expect this kind of object. They expect a request body type, but for these calls we can actually just omit this argument altogether. I have a fix for this that I've tested.

Versions

Octokit.net 6.2.1

Relevant log output

No response

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