Let's enable the 'gitaly_upload_pack_filter' feature flag
by default to let people test partial clone out of the box.

They can still turn it off manually if they want to disable
it in case of abuse, performance issue or policy decision.

Part of: https://gitlab.com/gitlab-org/gitaly/-/issues/2553
Part of: https://gitlab.com/gitlab-org/git/-/issues/56