Fix the send button tooltip (#326)

* Restore the helper text in input

* Revert "Restore the helper text in input"

This reverts commit f59ed7d.

* Initialize the tooltip on the send button

Author: brichet

packages/jupyter-chat/src/components/input/buttons/send-button.tsx

@@ -48,6 +48,9 @@ export function SendButton(
     };
     model.configChanged.connect(configChanged);
 
+    // Initialize the tooltip.
+    configChanged(model, model.config);
+
     return () => {
       model.valueChanged.disconnect(inputChanged);
       model.attachmentsChanged?.disconnect(inputChanged);