de, et, fr, pt_BR, uk: please fix ksnakeduel manual using outdated &ksnake; entity

[Friedrich W. H. Kossebau]

Hi,

KDocTools for KF6 has seen a clean-up for deprecated entities
(see https://invent.kde.org/frameworks/kdoctools/-/merge_requests/34/diffs)

As there is no warning system on the use of deprecated entities, this might 
result in some breakages once switching to KF6 KDocTools, uncovering the use 
of those outdated entities.

One example just found is that some translations of the KSnakeDuel manual 
still are using the long outdated entity referring to the former name, 
&ksnake; (original docbook does not have it).
Which results in the wrong name "KSnake" now in KF5 times.
As well as failing manual generation in KF6 times due to the then unknown 
entity.

Sorry for using global email instead of doing the work to file a bug for all 
the teams this time (also might be interesting to others to be aware about the 
clean-up of entities for KF6).

Cheers
Friedrich