[payment] GitHub: Ignore all "free tier" plans

[geropl]

Description

For years already, we don't store "free" subscriptions in the DB anymore, but assume those implicitly - except for those synced from GitHub. This gets in our way now as we want to move to Pay-as-you-go (epic).

This PR stops the syncing of GitHub subscriptions of those plans. Next step afterwards is to remove them from the database.

Related Issue(s)

Fixes #

How to test

Release Notes

NONE

Documentation

Build Options:

• /werft with-github-actions
  Experimental feature to run the build with GitHub Actions (and not in Werft).
• leeway-no-cache
  leeway-target=components:all
• /werft no-test
  Run Leeway with --dont-test

Publish Options

• /werft publish-to-npm
• /werft publish-to-jb-marketplace

Installer Options

• with-ee-license
• with-slow-database
• with-dedicated-emulation
• with-ws-manager-mk2
• workspace-feature-flags
  Add desired feature flags to the end of the line above, space separated

Preview Environment Options:

• /werft with-local-preview
  If enabled this will build install/preview
• /werft with-preview
• /werft with-large-vm
• /werft with-gce-vm
  If enabled this will create the environment on GCE infra
• /werft with-integration-tests=all
  Valid options are all, workspace, webapp, ide, jetbrains, vscode, ssh