backpatch to v11? Add "B" suffix for bytes to docs

I suggest this should be backpatched ?

commit 36e9d413a1d6928cd809d302d495fd6880a44b1e
Author: Greg Stark <stark@mit.edu>
Date:   Sat Oct 6 13:03:43 2018 -0400

    Add "B" suffix for bytes to docs
    
    6e7baa3227 and b06d8e58b5 added "B" as a valid suffix for
    GUC_UNIT_BYTES but neglected to add it to the docs.

 doc/src/sgml/config.sgml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)