[FIX] partner_autocomplete: Prevent unnecessary input field display for Mobile

Steps to Reproduce:
1. Install Sales module
2. Create a new quotation in mobile view

Issue:
- The input field of contact is displayed twice due to a missing `t-else`
  condition, causing both fields to appear simultaneously.

Solution:
- Added the missing `t-else` condition to ensure that only one input field is
  displayed as intended.

opw-4767186

closes odoo#210909

X-original-commit: c032778
Signed-off-by: Ricardo Gomes Rodrigues (rigr) <rigr@odoo.com>
Signed-off-by: Dhwani Patel (dwa) <dwa@odoo.com>

Author: dwa-odoo

addons/partner_autocomplete/static/src/xml/partner_autocomplete.xml

@@ -40,7 +40,7 @@
 
     <t t-name="partner_autocomplete.PartnerAutoCompleteMany2XField" t-inherit="web.Many2XAutocomplete" t-inherit-mode="primary">
         <xpath expr="//AutoComplete" position="replace">
-            <PartnerAutoComplete
+            <PartnerAutoComplete t-else=""
                 value="this.props.value || ''"
                 autoSelect="true"
                 sources="sources"