support request: fix form enctype

https://www.erp5.com/documentation/developer/guideline/module/erp5-Guideline.Module.Creation#set-form-encytype-to-multipart/form-data-when-using-file-upload

as a result, attaching files when submitting support request was not working

bt5/erp5_officejs_support_request_ui/SkinTemplateItem/portal_skins/erp5_officejs_support_request/SupportRequestModule_viewSupportRequestFastInputDialog.xml

@@ -53,7 +53,7 @@
         </item>
         <item>
             <key> <string>enctype</string> </key>
-            <value> <string></string> </value>
+            <value> <string>multipart/form-data</string> </value>
         </item>
         <item>
             <key> <string>group_list</string> </key>