Disable event encryption for reactions
Disable event encryption for reactions

For reactions, there is a very little gained by encrypting the entire event, as
relation data is already kept in the clear. Event encryption for a reaction
effectively only obscures the event type, but the purpose is still obvious from
the relation data, so nothing is really gained. It also causes quite a few
problems, such as:

  * triggers notifications via default push rules
  * prevents server-side bundling for reactions

The reaction key / content / emoji value does warrant encrypting, but this will
be handled separately by encrypting just this value.

See https://github.com/matrix-org/matrix-doc/pull/1849#pullrequestreview-248763642
Fixes https://github.com/vector-im/riot-web/issues/10130

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