Out-of-date usage of `generateAuthorizationServerMetadata` in README

Hello!

The section of the readme `#### Authorization server metadata` includes a reference to `generateAuthorizationServerMetadata`, which seems to no longer be present

Then there's `generateClerkAuthorizationServerMetadata` which seems to be have been replaced by `fetchClerkAuthorizationServerMetadata`.

I will try to put up a PR today but I need to get to lunch because I'm hungry.