Fix the repo name calculation logic in the Updoc CI workflow

[ulucinar]

Description of your changes

As we moved the official providers upbound/provider-{aws, azure, azuread, gcp} to their homes crossplane-contrib/provider-upjet-{aws, azure, azuread, gcp}, we will need to fix/change the provider repo name calculation in the reusable Updoc workflow so that we still compute the old repo names for these providers. This is required because although we have moved these providers to new repositories, the published package names are kept intact for backwards compatibility reasons.

I have:

• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Tested the changes proposed in this PR here: https://github.com/ulucinar/uptest/actions/runs/8283714517/job/22667549446

Please note that even if we pass provider-aws or provider-upjet-aws, the calculated package names are as expected, e.g., provider-aws-ec2.

[sergenyalcin]

Thanks @ulucinar LGTM!