fix: error if a11y support changed before ready

[codebytere]

Description of Change

Resolves #16256.

Starting with v4.0.0, app.setAccessibilitySupportEnabled() can only be called after the ready event is emitted. This clarifies that in documentation and ensures that an error is thrown so the method does not crash.

/cc @deepak1556

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Throw an error if app.setAccessibilitySupportEnabled() is called before the ready event is emitted.

[jkleinsc]

LGTM

[jkleinsc]

Merging as arm failure is unrelated to change (and broken in master).

[release-clerk]

Release Notes Persisted

Throw an error if app.setAccessibilitySupportEnabled() is called before the ready event is emitted.

[trop]

I have automatically backported this PR to "4-0-x", please check out #16268