Only update m.accepted_terms if there were changes
Only update m.accepted_terms if there were changes

Fixes https://github.com/vector-im/riot-web/issues/10744
matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk