docs(dpkg): update general commentary

Co-authored-by: Koichi Murase <myoga.murase@gmail.com>

Author: scop

completions/dpkg

@@ -1,4 +1,4 @@
-# This function is required by _dpkg and _dpkg-reconfigure -*- shell-script -*-
+# dpkg(1) and related commands completion                  -*- shell-script -*-
 
 if _comp_have_command grep-status; then
     _comp_xfunc_dpkg_installed_packages()
@@ -124,8 +124,6 @@ _comp_cmd_dpkg()
 } &&
     complete -F _comp_cmd_dpkg dpkg dpkg-deb dpkg-query
 
-# Debian GNU dpkg-reconfigure(8) completion
-#
 _comp_cmd_dpkg_reconfigure()
 {
     local cur prev words cword comp_args