fix: return updated `agent_card` in `JsonRpcTransport.get_card()`#552

sokoliva merged 4 commits intoa2aproject:maina2aproject/a2a-python:mainfrom

ShishirRmc:fix/jsonrpc-get-card-return-valueShishirRmc/a2a-python:fix/jsonrpc-get-card-return-valueCopy head branch name to clipboard