Clarify about evaluating the `comment` ”symbol” itself

This issue on Calva https://github.com/BetterThanTomorrow/calva/issues/1273 notes that you get an error when evaluating the `comment` word.

I think the solution is to try clarify that this is expected behaviour. Maybe somewhere here:

https://github.com/BetterThanTomorrow/dram/blob/f4266fddfcf25849e96465917c34abea078dfef3/drams/calva_getting_started/hello_repl.clj#L199

Read drams/calva_getting_started/hello_repl.clj around line 199 and review the related Calva issue #1273. Clarify in the guide that evaluating the `comment` symbol produces an error because it is expected behavior. Done when the explanation is clear to readers following the REPL guide.

Written by the indexing model from the issue text.