Previously, include actions include_dir, include_if_exists, and include
listed commented-out values which were not the defaults, which is
inconsistent with other entries.  Instead, replace them with '', which
is the default value.
Reported-by: Emanuel Araújo
Discussion: https://postgr.es/m/CAMuTAkYMx6Q27wpELDR3_v9aG443y7ZjeXu15_+1nGUjhMWOJA@mail.gmail.com
Backpatch-through: 9.4
 # These options allow settings to be loaded from files other than the
 # default postgresql.conf.
 
-#include_dir = 'conf.d'                        # include files ending in '.conf' from
-                                       # directory 'conf.d'
-#include_if_exists = 'exists.conf'     # include file only if it exists
-#include = 'special.conf'              # include file
+#include_dir = ''                      # include files ending in '.conf' from
+                                       # a directory, e.g., 'conf.d'
+#include_if_exists = ''                        # include file only if it exists
+#include = ''                          # include file
 
 
 #------------------------------------------------------------------------------