Fix untranslatable label.

Column label "Qty" of the symbol fields editor is translatable now.

(cherry picked from commit e7b9b0e)

eeschema/dialogs/dialog_fields_editor_global.cpp

@@ -161,7 +161,7 @@ public:
     wxString GetColLabelValue( int aCol ) override
     {
         if( aCol == QUANTITY_COLUMN )
-            return _T( "Qty" );
+            return _( "Qty" );
         else
             return m_fieldNames[ aCol ];
     }