[LangRef] Drop misleading anecdote

`shl nsw i8 1, i8 8` is poison, but `mul i8 1, i8 128` is not.

This was discussed previously here:
http://lists.llvm.org/pipermail/llvm-dev/2015-April/084195.html.  From
the discussion, it was not clear which semantics we want for `shl`, but
for now at least make the language reference more accurate.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286785 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed