erp5_corporate_identity: decrease the skin priority

Usually, skin priority of 50 or more is reserved for project customisations

bt5/erp5_corporate_identity/SkinTemplateItem/portal_skins/erp5_corporate_identity.xml

@@ -31,7 +31,7 @@
         </item>
         <item>
             <key> <string>business_template_skin_layer_priority</string> </key>
-            <value> <float>50.0</float> </value>
+            <value> <float>5.0</float> </value>
         </item>
         <item>
             <key> <string>id</string> </key>