Simplify task modal by removing redundant cancel button

Remove duplicate "Annuler" button from the Task creation/editing modal to improve UI clarity.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: d7bae60c-959e-464e-9a81-d3f674984466
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/d7bae60c-959e-464e-9a81-d3f674984466/S7zPZtF

client/src/pages/Tasks.tsx

@@ -135,20 +135,7 @@ function TaskFormInline({ task, onClose }: any) {
           📅 Date de début = Quand la tâche devient visible<br/>
           ⏰ Date d'échéance = Quand la tâche doit être terminée
         </p>
-        <button
-          type="button"
-          onClick={onClose}
-          style={{
-            float: 'right',
-            padding: '8px 16px',
-            border: '1px solid #d1d5db',
-            borderRadius: '0px',
-            backgroundColor: 'white',
-            cursor: 'pointer'
-          }}
-        >
-          Annuler
-        </button>
+
       </div>
 
       <form onSubmit={handleSubmit} style={{ display: 'flex', flexDirection: 'column', gap: '20px' }}>