Remove Data Deep Merge opt-out

[zachleat]

Originally introduced as a mechanism to ease 1.0 upgrade breaking change, probably okay to get rid of it now

Docs: https://www.11ty.dev/docs/data-deep-merge/

Please upvote or downvote with emoji reaction

[zachleat]

Zero downvotes on this one so far 😅

Thanks for weighing in, y’all

[zachleat]

This will swap the configuration API method to throw an error if passed false

// Same as default
eleventyConfig.setDataDeepMerge(true);
// Will throw an error in v4
eleventyConfig.setDataDeepMerge(false);