[FIX] web: ListView: correctly position no content helper

Before this commit, the no content helper was displayed just
below the control panel in empty list views, whereas it must be
displayed approximately in the middle of the screen.

The `position: relative` has been introduced recently, and doesn't
seem useful, so we simply remove it.

closes odoo/odoo#101108

X-original-commit: ee18aa1f6b85eb420e198775592a9e0772cc8475
Signed-off-by: Pierre Paridans (app) <app@odoo.com>
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>

addons/web/static/src/views/list/list_renderer.xml

@@ -3,7 +3,7 @@
 
     <t t-name="web.ListRenderer" owl="1">
         <div
-            class="o_list_renderer o_renderer position-relative"
+            class="o_list_renderer o_renderer"
             t-att-class="{'table-responsive': showTable}"
             t-attf-class="{{ props.archInfo.className or '' }}"
             tabindex="-1"