Need to take SAP-docs org owners into account in disallowed checks

[qmacro]

This PR SAP-docs/btp-business-application-studio#14 caused a 'disallowed content' message to be generated. This is because the PR author @Shegox is not in the repo's admin team. We should extend the membership check to take into account organisation level members.

[Shegox]

As a potential solution would be replacing the whole check with check, which determines if a user has admin/write (depending on what we want) permissions to the repository via https://docs.github.com/en/rest/reference/repos#get-repository-permissions-for-a-user

[qmacro]

Thanks @Shegox, this is a great suggestion, and means we only need to make one check (one API call).