Add support for raw template URL in clusterctl generate yaml

[DannyBrito]

User Story

As a user I would like to use clustertctl generate yaml --from with a URL to a raw template.

Detailed Description

At the moment clusterctl generate yaml --from accepts only GitHub.com URLs

Anything else you would like to add:

when running clustertcl generate yaml --help the example convey the idea that it accepts any URL.

  # Generates a configuration file with variable values using
  a template from a specific URL.
  clusterctl generate yaml --from https://github.com/foo-org/foo-repository/blob/main/cluster-template.yaml

/kind feature

[sbueringer]

/area clusterctl

[fabriziopandini]

/triage accepted
/help wanted

[aniruddha2000]

/assign

[aniruddha2000]

I think this piece of code is causing the issue.