Inline allOf parameters are always not required

Fixes https://github.com/OpenAPITools/openapi-generator/issues/14163

I tried writing a test instead of editing the samples such as below. The test succeeded with or without the change, which is strange because I can see the change is working as intended. openAPI.toString() returns the same thing before and after the change.

CSharpModelTest.java

    @Test
    public void assertAllOfIsRequired() {
        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/csharp-netcore/issue_14163.yaml");
        CSharpNetCoreClientCodegen codegen = new CSharpNetCoreClientCodegen();
        codegen.setOpenAPI(openAPI);
        PathItem pathItem = openAPI.getPaths().get("/country");
        Operation operation = pathItem.getPost();
        String requiredParameter = (String) openAPI.getComponents().getSchemas().get("getCountry_request_allOf").getRequired().get(0);
        Assert.assertEquals(requiredParameter, "country");
    }

src/test/resources/3_0/csharp-netcore/issue_14163

openapi: 3.0.1
info:
  title: country
  version: 0.0.0
paths:
  "/country":
    post:
      operationId: getCountry
      requestBody:
        content:
          application/x-www-form-urlencoded:
            schema:
              allOf:
              - required:
                - country
                type: object
                properties:
                  country:
                    type: string
      responses:
        '200':
          description: OK

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