Geo: Document the 2 versions of project repo replication based on FFs

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With the introduction of a new version of project repository replication - that replicates project repositories only when the Git repository exists, behind the feature flag geo_project_repository_replication_v2, we will have two code paths.

• Document the 2 versions of project repo replication based on FFs.
• Document that geo_project_repository_replication_v2 takes priority if both are enabled at the same time
• Eventually the code path behind the first version geo_project_repository_replication will be deprecated, but the FF will exist, and will combine the use of both the FFs. At this point, we will remove geo_project_repository_replication_v2