docs: Drop the HyLambdaListKeyword docs

HyLambdaListKeyword was removed a while ago, drop its documentation too.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge pull request #698 from algernon/h/docs/no-lambdalistkeywords

docs: Drop the HyLambdaListKeyword docs