Remove string attribute from views

issue2350

view/product_supplier_weekday_form.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
 this repository contains the full copyright notices and license terms. -->
-<form string="Week Day">
+<form>
     <label name="product_supplier"/>
     <field name="product_supplier"/>
     <newline/>

view/product_supplier_weekday_tree.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <!-- 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 string="Week Day">
+<tree>
     <field name="product_supplier"/>
     <field name="weekday"/>
 </tree>

view/product_supplier_weekday_tree_editable.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <!-- 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 string="Week Day" editable="bottom">
+<tree editable="bottom">
     <field name="product_supplier"/>
     <field name="weekday" expand="1"/>
 </tree>