[Form] Update minimal requirement in composer.json

Minimal requirement for PropertyAccess component needs to be `~2.3` as Form component depends on new method `PropertyAccess::createPropertyAccessor()`
bug #9960 [Form] Update minimal requirement in composer.json (stloyd)

This PR was merged into the 2.3 branch.

Discussion
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[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()`.

Commits
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88153b3 [Form] Update minimal requirement in composer.json