Block Library: unwrap Classic block migration notice experiment

[im3dabasia]

Please note

Note: This PR is part of Experiment 1 (WP 7.1 Classic block deprecation, #78067) and may need updates as the experiment evolves, particularly when additional migration paths for existing Classic block instances are finalized. This PR can be amended or followed up on before the experiment is ready to fully launch.

What?

Follow up to #78090

Removes the gutenberg-classic-block-deprecation experiment gate so the Classic block migration notice ships to all users by default.

Why?

• The migration notice landed behind an experiment flag in Experiment: Add Classic block migration notice #78090.
• It's ready to ship to everyone as part of the Classic block deprecation () Block Library: Deprecate Classic Block and TinyMCE #78067.

Testing Instructions

1. In Code Editor paste <!-- wp:freeform --><p>Hello</p><!-- /wp:freeform -->, switch to Visual editor.
2. Confirm deprecation warning appears with "Convert to blocks" and "Convert to Custom HTML" buttons.
3. Test both buttons convert content correctly.
4. Confirm experiment no longer appears on the Gutenberg Experiments admin page.

[im3dabasia]

Note: This PR is part of Experiment 1 (WP 7.1 Classic block deprecation, #78067) and may need updates as the experiment evolve, particularly when additional migration paths for existing Classic block instances are finalized. This PR can be amended or followed up on before the experiment is ready to fully launch.

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Co-authored-by: im3dabasia <[email protected]>
Co-authored-by: tyxla <[email protected]>
Co-authored-by: yuliyan <[email protected]>

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[yuliyan]

@im3dabasia, Thanks for the contribution!

I think it's a little too early to unwrap this experiment though, especially since it hasn't even shipped in a release yet.

We’d like to give it a bit more time to bake - review the user-facing copy, gather feedback from users, and potentially iterate on the experience before making it the default for everyone.

Also, it looks like one of the e2e tests is currently failing.

[tyxla]

Agreed with @yuliyan. It's a bit early to unwrap; we'd like to ship this as an experimend and run with it for a while, while also getting feedback and improving it on the way. Unwrapping the experiment is the last step when we're confident that the experiment is doing well and is ready for production.

[im3dabasia]

Sure, I am aligning with your opinions. I will update this PR once we are ready to unwrap this experiment and roll it out live for everyone in the GB plugin. Thanks for the quick reviews. I really appreciate them!

[tyxla]

Thanks again for your work here @im3dabasia!

I'm doing a last test/review pass on this one and will proceed with shipping so we can include it in WordPress 7.1.

[tyxla]

LGTM, thanks again @im3dabasia 🙌

[im3dabasia]

Thanks @tyxla for taking forward this PR. I really appreciate it! Have a good day!