Remove Semantic Forms Select extension

[yaronkoren]

There are a number of similarities here to the situation with Semantic Tasks, which I also want to remove (see #473), though Semantic Forms Select is in a less extreme position. But like Semantic Tasks, Semantic Forms Select:

• does not fully work with the latest code - in this case, there seem to be at least some problems with recent Page Forms versions, according to this
• has not had a new version in a long time - it's currently stuck at 4.0.0-beta, and the last version officially released was apparently 3.0.0, back in 2018
• was only added to Canasta in 2023 - see Adds SemanticFormsSelect extension #248
• gets a low amount of usage, it appears - though SFS, unlike ST, is found in wiki farms and packages other than Canasta.

See #248 also for my own views on Semantic Forms Select (I am skeptical, and I think that basically everything it does can be done directly with Page Forms). I said at the time that the case for including SFS was in large part because it can't be installed without using Composer, which makes it difficult for Canasta admins to install separately. But we know the way to fix this: its extension requirements (SMW and PF) should be removed from composer.json, i.e. lines 42 and 42 should be removed here. Hopefully we can get the SMW developers to at least make this one change to the SFS code. (As a side note, I'm not sure whether SFS is currently being installed correctly in Canasta, for that same reason... what a headache.)