Use char widget on translation list

This improve the performance on tryton as it can then use fixed column.

issue6697
review39591002

trytond/ir/view/translation_list.xml

@@ -2,8 +2,8 @@
 <!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
 this repository contains the full copyright notices and license terms. -->
 <tree editable="bottom">
-    <field name="src"/>
-    <field name="value"/>
+    <field name="src" widget="char"/>
+    <field name="value" widget="char"/>
     <field name="fuzzy"/>
     <field name="name"/>
     <field name="lang"/>