fix: use wildcard for github domain validation

[lpbedard]

Github recently added a new subdomain release-assets to their githubusercontent.com creating an issue when validating the incoming requests.

This PR updates the validation on the domain name instead of the full subdomain.domain

Message from github:

Thank you for reaching out to GitHub Support!
I checked in with our engineering teams about this.
That’s correct, we have recently turned on a feature flag that adds the address release-assets.githubusercontent.com for release assets.
This change comes a part of some internal service updates and is planned to be permanent.
The *.githubusercontent.com address is listed as a wildcard in the GitHub META API Endpoint and depending on the activity performed you may see connections to many different githubusercontent.com subdomains, with some of them being new from time to time.