Update lyx-2.4 docs

[Jürgen Spitzmüller]

Am Sonntag, dem 29.01.2023 um 17:23 +0100 schrieb Jean-Pierre Chrétien:
> I would like to search easily what has been updated since (but for
> the new index 
> features that I have  already updated in the UserGuide).
> Is it possible to search for modifications after a given date in the
> documents ?
> I could search for changes in Trac, but is is quite lengthy.

Document > Track Changes > Accept and Reject Changes. This dialog has
the change dates (not ideal for sure).

-- 
Jürgen