Draft: docs: document Geo project repo replication versions

Relates to issue 550191

This MR was created by Duo in Session 1238440

Changes

• Document the two versions of project repository replication based on feature flags
• Document that geo_project_repository_replication_v2 takes priority when both feature flags are enabled
• Document the eventual deprecation path for geo_project_repository_replication feature flag
• Update Geo documentation to clarify the behavior of both replication versions