BREAKING CHANGE: Remove send_event_error
BREAKING CHANGE: Remove send_event_error

Reverts https://github.com/matrix-org/matrix-js-sdk/pull/378

This swallowed all errors from sendEvent, breaking the ICE candidate
retrying. react-sdk no longer listens for send_event_error so I
think it's best to just remove this.

krombel/matrix-js-sdk,krombel/matrix-js-sdk,krombel/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk