Use hydra semantics for unknown room versions (#4957)
This inverts the check for whether to use hydra semantics to only NOT use
it for known, old room versions and use hydra for everything else, so
rooms with versions we don't know about will use hydra semantics.
This will cause any rooms using old/experiental versions unknown to
the js-sdk to break, but will mean that wehn the next room version
comes out, we'll use hydra for it which is, of course, not a given,
but is way more likely than going back to the old semantics.
The mobile Element clients currently hardcode hydra versions (ie.
as it is without this change, but we expect them to make this same
change soon after the hydra release.
We do NOT expect this to land with the hydra release, but target it for
the release after.
Reverts 1e5054a8ff87f83b0875916aa16f435853bf165a from https://github.com/matrix-org/matrix-js-sdk/pull/4937
See https://github.com/element-hq/element-meta/issues/2921 for public
discussion.
