Rewise vamdc dependency install instructions once upstream is updated

https://astroquery.readthedocs.io/en/latest/vamdc/vamdc.html currently asks for install from fork rather than a released version. Ideally this should change.

Open the VAMDC documentation page at https://astroquery.readthedocs.io/en/latest/vamdc/vamdc.html and first verify that the upstream dependency has a released version. Once it is available, update the installation instructions to use that release instead of the fork; done means the page no longer directs users to install from the fork.

Written by the indexing model from the issue text.