fix google-beta provider source info

[daniel-cit]

This pull request Fixes #359

google-beta provider was pointing to the wrong source in the version.tf files:

It was:

    google-beta = {
      source  = "hashicorp/google"
      version = ">= 3.50"
    }

but it must be:

    google-beta = {
      source  = "hashicorp/google-beta"
      version = ">= 3.50"
    }