[FIX] mail: Left border of the 'send' button is missing after clicking on it

Before this commit:
When we click on 'send' and 'log,' the left border disappears for
a short while.

After this commit:
The left border on the 'send' and 'log' buttons is visible even after
clicking on them.

task-3549138

closes odoo/odoo#138513

X-original-commit: ec42f19ad2996f1c471ea520ce0211f4d9e2ab0a
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/core/common/composer.xml

@@ -102,7 +102,7 @@
 </t>
 
 <t t-name="mail.Composer.sendButton">
-    <button t-if="!compact or ui.isSmall" class="o-mail-Composer-send btn o-last border-start-0"
+    <button t-if="!compact or ui.isSmall" class="o-mail-Composer-send btn o-last"
         t-att-class="{'btn-primary': extended, 'rounded-0 rounded-end-3': !extended and !compact, 'btn-link align-self-stretch': !extended, 'border-start-0 ms-2 me-3': env.inDiscussApp}"
         t-on-click="sendMessage"
         t-att-disabled="isSendButtonDisabled"