SEP-12 PUT should accept response of 200

In packages/demo-wallet-shared/methods/sep12/putSep12FieldsRequest.ts

It expects a response of 202. But 200 is also an acceptable response. Let's handle this case

https://github.com/stellar/stellar-protocol/commit/2d46fe87fa9aa512610078eda51dc52573ed754b#diff-1dc2bdae0cffb9fccb696891fb59ca6533c8ab3a026bb60b9249cb6fce549d1dR311