Amazon Q chat, "shift+enter" sends message when using US international layout

## Problem

On MacOS, I'm using a US keyboard with a "US-international - PC" layout. For some keys (quote, double quote, backtick and a few other) this keyboard layout waits before fully inserting the key, so that "`" followed by "e" results in "è". To insert an individual backquote you can either follow it with a , or just with something that doesn't combine with the backtick.

As the sequence to start a code block is three backticks ```, the keyboard sequence that works in most editors to do that is

``

However in the Amazon Q chat the `` at the end is interpreted by the chat as , hence committing the message to the chat, instead of starting a new line.

``

At that point you were in the middle of explaining something to Q, so you need to stop whatever processing it started doing, copy your whole message because you can't edit it, and then restart again.

The only way to go around it is to add an extra in your sequence, but that's not the normal keyboard behaviour

``

## Steps to reproduce the issue

- Using a US keyboard
- Set the keyboard layout to US-International PC

- Open the Amazon Q chat
- Try to start a code block with ``

## Expected behavior
The message editor should start a code block and move to the next line, instead the message is sent to Q.

## System details (run `AWS: About` and/or `Amazon Q: About`)

- OS: MacOS
- Visual Studio Code version: 1.99.3
- AWS Toolkit version: 3.59.0
- Amazon Q version: 1.65.0

Reproduce the issue in the Amazon Q chat on macOS with the US-International PC layout, using three backticks followed by Shift+Enter. Trace the chat message editor's handling of that key sequence and verify that it inserts a new line and starts a code block without sending the message.

Written by the indexing model from the issue text.