fix: render arrays with boolean false item schemas

[cyphercodes]

Description

Guard the array item schema type lookup so JSON Schema boolean schemas such as items: false do not throw while rendering nested array parameters.

Adds a regression test for an OpenAPI 3.1-style tuple schema using prefixItems with items: false.

Motivation and Context

Fixes #10921.

OpenAPI 3.1 uses JSON Schema 2020-12, where tuple schemas can disallow additional items with items: false. Rendering the parameter form reached schemaItems?.get("type"); because boolean schemas do not implement get, the endpoint details crashed instead of rendering.

How Has This Been Tested?

• npm run test:unit -- --runTestsByPath test/unit/core/plugins/json-schema-5/components/json-schema-form.jsx --runInBand
• ./node_modules/.bin/eslint --quiet src/core/plugins/json-schema-5/components/json-schema-components.jsx test/unit/core/plugins/json-schema-5/components/json-schema-form.jsx
• git diff --check

Screenshots (if appropriate):

N/A

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

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