* Arrange a few titles
Before this change, PublicRoomsChunk in the spec text could be found in
two places (actually three but the third one is identical to the first
one), defining two (_mostly_ identical but) different schemas.
Ctrl-F'ing through the spec may confuse you with the "wrong" definition.
This commit gives distinct schemas distinct names; aside from
PublicRoomChunk, the same story happens with the derivative of
stripped_state.yaml used in space_hierarchy.yaml (it's not exactly
StrippedStateEvent either).
As for the removal of `PublicRoomsChunks` (plural) - this title is
unnecessary because the tooling would place rather self-explanatory
`[PublicRoomsChunk]` without it, whereas the plural title ends up with
no definition in the spec text.
* Add changelog
6adacd18c1