docs: Attempt to fix PR14053.

docs: Attempt to fix PR14053.

Hypothesis 1: use of `.. code::` directive instead of `.. code-block::`
is causing Sphinx to discard the block. On my machine, `.. code::`
renders fine. However, I don't think that `..  code::` is actually a
legit Sphinx directive. I believe that on my machine Sphinx is falling
back to just displaying it monospace with no syntax, whereas llvm.org's
Sphinx is just discarding it.

This is truly "remote debugging" since I can't reproduce this on my
machine. It would be helpful to be able to see the llvm.org Sphinx
build logs; if that's possible please let me know.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165632 91177308-0d34-0410-b5e6-96231b3b80d8