depr: nullable_type_declaration_for_default_null_value - deprecate option that is against @PHP84Migration

[keradus]

ref #7774

[coveralls]

coverage: 96.034%. remained the same
when pulling 82c8ea0 on keradus:depr
into 54e8f39 on PHP-CS-Fixer:master.

[Wirone]

FYI: I've changed chore to feat, because SemVer specifies it explicitly that deprecations in public API have to change minor version, so basically it's a feature ("net negative", but still).

[keradus]

OK that deprecation is bumping minor in SemVer.
wondering if feat category fits best, maybe we shall have dedicated depr category. we will deprecate more things soon and see them in features section of release changelog may be coubter-intuitive

[Wirone]

IMHO if there's "deprecate" in the title then it's enough. For automated release notes maybe depr: or feat(depr): will be required, but we're not there yet.

[keradus]

let me go with depr variant then.