fix organization model struct

[bodepd]

when making the following call, which returns the current organization:

result, err := s.sfxClient.GetOrganization(s.ctx, "")

It fails with the following error:

panic: json: cannot unmarshal bool into Go struct field Organization.accountRenews of type string

This patch changes the type of accountRenews to be a bool so that I can use the GetOrganization methods.

[benkeith-splunk]

@bodepd thanks for fixing this, not sure why it was ever set to string in the first place.