[12.x] Clarify where the code should be placed (#10423)

* Clarify where the code should be placed

* Update context.md

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Co-authored-by: Taylor Otwell <taylor@laravel.com>

Author: AhmedAlaa4611

context.md

@@ -227,6 +227,7 @@ Stacks can be useful to capture historical information about a request, such as
 use Illuminate\Support\Facades\Context;
 use Illuminate\Support\Facades\DB;
 
+// In AppServiceProvider.php...
 DB::listen(function ($event) {
     Context::push('queries', [$event->time, $event->sql]);
 });