Default enable feature flag for Duo Developer

What does this MR do and why?

This MR default enables the feature flag duo_developer_button. It is globally enabled for everyone on .com for this week. duo_developer_button controls the switch to use developer/v flow (based on flow registry) or issue_to_merge_request flow (older configuration)

References

FF rollout issue - #579076

Screenshots or screen recordings

Before	After

How to set up and validate locally

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