Enable route_hll_to_snowplow_phase2 FF by default

What does this MR do and why?

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/363562 and #362274 (closed)

We've finished evaluating route_hll_to_snowplow_phase2 in production and ready to enable it by default.

Will consider removing (or changing type to ops) in the next milestone.

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