[Form] Update minimal requirement in composer.json

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Tests pass?   | yes
| Fixed tickets | #9959
| License       | MIT

Minimal requirement for PropertyAccess component needs to be `~2.3` as Form component depends on new method `PropertyAccess::createPropertyAccessor()`.