Remove prettier.doc.builders.concat

[fisker]

Description

Ref #13142

Checklist

• I’ve added tests to confirm my change works.
• (If changing the API or CLI) I’ve documented the changes I’ve made (in the docs/ directory).
• (If the change is user-facing) I’ve added my changes to changelog_unreleased/*/XXXX.md file following changelog_unreleased/TEMPLATE.md.
• I’ve read the contributing guidelines.

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[fisker]

Should we remove it "softly" const concat = parts => parts?

[sosukesuzuki]

Update commands.md and add changelog?

[fisker]

@thorn0 #13203 (comment)

[thorn0]

Should we remove it "softly" const concat = parts => parts?

Yes, let's do this.

[thorn0]

Otherwise for many plugins it might be the only breaking change. With this soft deprecation, there is a good change those plugins won't need to be changed at all.

[fisker]

Should we change this line

prettier/src/document/constants.js

Line 2 in e096ea7

export const DOC_TYPE_CONCAT = "concat";

to anther string?

Otherwise,

{
	type: 'concat'
}

Will pass the doc type check, but fail when calling array methods.

[thorn0]

Let's use "array".