chore(codegen): update smithy to 1.56.0

[trivikr]

Issue

Internal JS-5849

Description

Updates smithy CLI to 1.56.0

Testing

CI

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[trivikr]

The HttpEmptyPrefixHeadersRequestClient protocol test is failing

 FAIL  test/functional/restxml.spec.ts > HttpEmptyPrefixHeadersRequestClient:Request
AssertionError: expected 'Hello' to be 'There' // Object.is equality

Expected: "There"
Received: "Hello"

 ❯ test/functional/restxml.spec.ts:1451:32
    1449| 
    1450|     expect(r.headers["hello"]).toBeDefined();
    1451|     expect(r.headers["hello"]).toBe("There");
       |                                ^
    1452|     expect(r.headers["x-foo"]).toBeDefined();
    1453|     expect(r.headers["x-foo"]).toBe("Foo");