docs: simplify call recipient example

[Si40Code]

Summary

• sync the CALL-E Developer API OpenAPI snapshot used by the SDK
• keep explicit recipient examples minimal by providing only the required phones field
• keep optional region and locale support unchanged

Compatibility

Documentation and example-only change. No runtime API or package behavior changes, and no package release is required.

Validation

• pnpm run validate
• 35 tests passed
• type checks, package smoke test, and tarball smoke test passed