[PATCH 3 of 4] i18n: omit redundant translatable synopsis text to avoid xgettext warning

[FUJIWARA Katsunori]

# HG changeset patch
# User FUJIWARA Katsunori <foozy at lares.dti.ne.jp>
# Date 1528687936 -32400
#      Mon Jun 11 12:32:16 2018 +0900
# Node ID ddfbcd8d9351fb699d08482d2ced0e6cc42ea319
# Parent  b2d92c607d9af9945a03cd2e5d781021bfc80de1
# Available At https://bitbucket.org/foozy/mercurial-wip
#              hg pull https://bitbucket.org/foozy/mercurial-wip -r ddfbcd8d9351
# EXP-Topic refactor-update-pot
i18n: omit redundant translatable synopsis text to avoid xgettext warning

This empty translatable synopsis text causes xgettext warning below:

    Empty msgid.  It is reserved by GNU gettext:
    gettext("") returns the header entry with
    meta information, not the empty string.

This "synopsis" argument of @command annotation is omitable.

diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -921,8 +921,7 @@ def debugfileset(ui, repo, expr, **opts)
         ui.write("%s\n" % f)
 
 @command('debugformat',
-         [] + cmdutil.formatteropts,
-        _(''))
+         [] + cmdutil.formatteropts)
 def debugformat(ui, repo, **opts):
     """display format information about the current repository