enbaling github-scaffolder plugin

[yray-pixel]

Issue

Fix FLPATH-4408 - GitHub autocomplete request fails at RHDH

Problem

When creating a new project in RHDH Conversion Hub, the GitHub repository autocomplete fails with a 400 error on
the "Source and target repositories" page.

Error:

POST /v2/autocomplete/github/repositoriesWithOwner
Response: 400 Bad Request
Error: "Unsupported provider: github"

Root Cause

The backstage-plugin-scaffolder-backend-module-github is disabled in our instance of RHDH's default configuration. This module provides the autocomplete endpoint for GitHub repositories. Without it enabled, GitHub is not recognized as a supported SCM provider for the scaffolder.

Works locally because packages/backend/src/index.ts directly imports the module, but RHDH uses dynamic plugin
configuration.

Changes

Enable the GitHub scaffolder backend module in dynamic plugins configuration:

[mareklibra]

This is weird, it used to work.
Approving since it has been tested. It will be replaced by #43 and redhat-developer/rhdh-plugins#3321 anyway where this integration works without the need for that explicit addition.