text: Title: Remove deprecated constructs from Libdoc spec files
  Body: `datatypes` were deprecated in favor of more generic `typedocs` in RF 5.0 (#4160) and in RF 6.1 there were argument type related changes (#4538). We have preserved old data in specs for backwards compatibility reasons but now it's time remove it. The main motivation is making specs simpler and smaller.
  
  Libdoc can read old specs. That support can still be preserved.