[FIX] web: fix datetime picker buttons overflowing

Before this commit, the "Apply" button in date pickers (not datetime)
would overflow from its popover in desktop view since its position is
set to absolute, and since there are no time pickers to extend the
height of the picker it simply overflows.

This commit ensures that the buttons are correctly displayed when there
are no time pickers.

Part-of: odoo/odoo#127734

addons/web/static/src/core/datetime/datetime_picker.xml

@@ -78,8 +78,10 @@
                     </t>
                 </t>
             </div>
-
-            <div t-attf-class="o_datetime_buttons position-md-absolute end-0">
+            <div
+                class="o_datetime_buttons end-0"
+                t-att-class="{ 'position-md-absolute': props.type === 'datetime'  }"
+            >
                 <t t-slot="buttons" />
             </div>
         </div>

addons/web/static/src/core/datetime/datetime_picker_popover.xml

@@ -4,8 +4,11 @@
         <DateTimePicker t-props="props.pickerProps">
             <t t-set-slot="buttons">
                 <t t-if="props.pickerProps.type === 'datetime' or Array.isArray(props.pickerProps.value)">
-                    <button class="o_apply btn btn-primary btn-sm w-100 w-md-auto" t-on-click="props.close">
-                        <i class="fa fa-check pe-1" />
+                    <button
+                        class="o_apply btn btn-primary btn-sm w-100 w-md-auto d-flex align-items-center justify-content-center gap-1"
+                        t-on-click="props.close"
+                    >
+                        <i class="fa fa-check" />
                         <span>Apply</span>
                     </button>
                 </t>