Fix wrong Japanese translation

Translation in Qt5 is already fixed
in qttranslations/16d5447febe09fcb44be6cdb77e03ffb80238bd9.

Task-number: QTBUG-44081
Change-Id: I114a402573f47df604d529407774d44ac3c419f1
Reviewed-by: Tasuku Suzuki <[email protected]>
Reviewed-by: Liang Qi <[email protected]>

Author: Takumi Asaki

translations/qt_ja.ts

@@ -2755,12 +2755,11 @@ Do you want to delete it anyway?</source>
     <name>QFontDatabase</name>
     <message>
         <source>Normal</source>
-        <translatorcomment>ここはどう訳すべきか...</translatorcomment>
-        <translation>明朝</translation>
+        <translation>標準</translation>
     </message>
     <message>
         <source>Bold</source>
-        <translation>ゴシック</translation>
+        <translation>太字</translation>
     </message>
     <message>
         <source>Demi Bold</source>