Spec refers to EDUs and account data as "events"

The C-S spec refers to things like [`m.receipt`](https://spec.matrix.org/unstable/client-server-api/#mreceipt) and [`m.typing`](https://spec.matrix.org/unstable/client-server-api/#mtyping), and various bits of account data as "events". I think this is confusing - it gives the impression that such objects can appear in a room timeline, which is not the case.

Search the Client-Server specification for uses of “events” describing m.receipt, m.typing, and account data, starting from the linked sections. Check how the specification distinguishes room-timeline events from EDUs and account data. Done means the terminology is corrected consistently without implying these objects can appear in a room timeline.

Written by the indexing model from the issue text.