fix(core): update Slack notification formatting to use bold correctly

app/Notifications/Database/BackupSuccess.php

@@ -77,7 +77,7 @@ class BackupSuccess extends CustomEmailNotification
         $title = 'Database backup successful';
         $description = "Database backup for {$this->name} (db:{$this->database_name}) was successful.";
 
-        $description .= "\n\n**Frequency:** {$this->frequency}";
+        $description .= "\n\n*Frequency:* {$this->frequency}";
 
         return new SlackMessage(
             title: $title,