[LangRef] Remove (non-normative) paragraph that doesn't make sense.

It appears to be referring to nonexistent entities. This must be a
carry-over from an older version of the document.

Patch by Mikael Lyngvig!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196342 91177308-0d34-0410-b5e6-96231b3b80d8