[FIX] mail: user signature

- Install Invoicing
- Multi company Set up with no common contact book
- Create & validate an invoice with user A in company 1
- Change to company 2 with user A
- Connect with user B in company 1
- Send & Print the invoice

An error is raised on the template rendering because user B cannot read
info from user A.

opw-1928676

closes odoo/odoo#30649

addons/mail/data/mail_data.xml

@@ -264,8 +264,8 @@
                 Best regards,
             </div>
             <div>&amp;nbsp;</div>
-            <div t-if="record.user_id and record.user_id.signature" style="font-size: 13px;">
-                <div t-raw="record.user_id.signature"/>
+            <div t-if="record.user_id and record.user_id.sudo().signature" style="font-size: 13px;">
+                <div t-raw="record.user_id.sudo().signature"/>
             </div>
         </td>
     </tr>