Update README.md to set expected_status to assert_response_schema_confirm explicitly.
Update README.md to set expected_status to assert_response_schema_confirm explicitly.

  - To resolve deprecation warning `[DEPRECATION] Pass expected response status code to check it against the corresponding schema explicitly.`.
  - After committee 4.4.0, `assert_response_schema_confirm` without expected_status raises deprecation warnings.
    - ref: https://github.com/interagent/committee/commit/9a388e5e6a5dfe2e4515b07bba5feaf496c83d4c
    - `[DEPRECATION] Pass expected response status code to check it against the corresponding schema explicitly.`
  - So this commit updates README.md to set expected_status(200) explicitly.

willnet/committee-rails,willnet/committee-rails