No need to advertise `conf`

conf is Saturnin's internal command to access common configuration.  It
could be, in theory, useful for end-user to investigate the configuration,
but they would already need to know how it works and which configuration
keypaths or sections they want to look at.

Bettter hide it; it's not worth for the potential confusion.

Note that the command could actually even be removed one day since
internally it's much more efficient to use saturnin__conf().

src/saturnin.sh.skel

     #
     # List subcommands
     #
-    echo conf
     find "$SATURNIN_LIBEXEC" \
         -mindepth 1 \
         -maxdepth 1 \

tests/cli/oracle/usage.stderr

   --version      show version and exit
 
 commands:
-  conf
   bar
   baz
   foo