Enable FF code_suggestions_include_context_imports by default

What does this MR do and why?

We introduced Imports as additional context to Code Suggestions behind the code_suggestions_include_context_imports FF. This change enables the FF by default, ensuring it applies to both SaaS and SM users.

This has already been rolled out globally in production. See #514124 (comment 2429432216)

References

• Rollout issue: [Feature flag] Rollout of `code_suggestions_inc... (#514124 - closed)
• Rollout updates issue: https://gitlab.com/gitlab-org/editor-extensions/gitlab-lsp/-/issues/775+ (see comment)
• Enablement go-ahead comment: gitlab-com/www-gitlab-com!138888 (comment 2441205085)

Screenshots or screen recordings

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How to set up and validate locally

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Related to #514124 (closed)