Default enable FF: code_suggestions_tokens_from_customers_dot

What does this MR do and why?

Enable code_suggestions_tokens_from_customers_dot by default.

This FF guards saving the JWT token from CDot during the SeatSyncLinkSync process.

No-op for SaaS, only SM instances are affected. The flag was only introduced during 16.3 dev.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/420599, #417762 (closed)

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