[Docs] Add missing <code> tags (minor)

These configs looked inconsistent from the rest.

Author: Andrew Or <andrewor14@gmail.com>

Closes #1936 from andrewor14/docs-code and squashes the following commits:

15f578a [Andrew Or] Add <code> tag

(cherry picked from commit e4245656438d00714ebd59e89c4de3fdaae83494)
Signed-off-by: Reynold Xin <rxin@apache.org>