[skip ci] Update .po files

Autobuild bot on TravisCI · Autobuild bot on TravisCI · commit b2b9ae9935b3 · 2018-12-25T15:17:44.000+09:00
diff --git a/reference/expressions.po b/reference/expressions.po
@@ -573,7 +573,7 @@ msgstr "サブジェネレータの委譲を簡単にするための、 :token:`
 
 #: ../../reference/expressions.rst:463
 msgid ":pep:`525` - Asynchronous Generators"
-msgstr ""
+msgstr ":pep:`525` - 非同期ジェネレータ"
 
 #: ../../reference/expressions.rst:463
 msgid ""
