We don't need to fake the ZIM installations anymore

[letompouce]

By the past, we used to keep uncompressed ZIM, which are then symlinked in place in order to improve ZIM installs speed

Since ideascube/catalog-i-o@3d9d2af we only use portable ZIM format.

Therefore, we don't neek to keep on trying to use these uncompressed ZIM files.

[letompouce]

It seems a207df9 deals with the removal of portable ZIM management. Therefore I don't remember what I had in mind when I wrote this issue? 😕