Commit 644f0d7c added logical replication message type enums to use
instead of character literals but some char substitutions were overlooked.

Author: Peter Smith
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CAHut+PsTG=Vrv8hgrvOnAvCNR21jhqMdPk2n0a1uJPoW0p+UfQ@mail.gmail.com