chore(codegen): sync for handling empty structure payloads

[smilkuri]

Issue

#7169

Description

What does this implement/fix? Explain your changes.

Testing

dev-dsk-smilkuri-1a-17aece6b % yarn lerna run test --scope '@aws-sdk/aws-protocoltests-restjson'
lerna notice cli v5.5.2
lerna notice filter including "@aws-sdk/aws-protocoltests-restjson"
lerna info filter [ '@aws-sdk/aws-protocoltests-restjson' ]
lerna info Executing command in 1 package: "yarn run test"
lerna info run Ran npm script 'test' in '@aws-sdk/aws-protocoltests-restjson' in 6.3s:

 RUN  v2.1.9 /local/home/smilkuri/aws-sdk-js-v3/private/aws-protocoltests-restjson

 ✓ test/functional/restjson1.spec.ts (240 tests | 10 skipped) 1893ms

 Test Files  1 passed (1)
      Tests  230 passed | 10 skipped (240)
   Start at  15:53:56
   Duration  3.52s (transform 879ms, setup 0ms, collect 1.34s, tests 1.89s, environment 0ms, prepare 96ms)

lerna success run Ran npm script 'test' in 1 package in 6.3s:
lerna success - @aws-sdk/aws-protocoltests-restjson

• [ ] Yet to fix the failing test RestJsonHttpPayloadWithStructureAndEmptyResponseBody:Response in @aws-protocoltests-restjson-schema

Additional context

Add any other context about the PR here.

Checklist

• [ ] If you wrote E2E tests, are they resilient to concurrent I/O?
• [ ] If adding new public functions, did you add the @public tag and enable doc generation on the package?

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