[a11y] Content of the in app help sheets is still read after closing it

[data-sync-user]

Important details:

• [macOS/Linux] use ESC button;
• [Windows] use mouse click;

Version/build found in:

• 2.21.0 (2.202402070704);

Reproducible on:

• desktop;

Prerequisites:

• Have the Mozilla VPN client installed;
• Be logged in with an account with subscription for Mozilla VPN;
• Have the default screen reader ON;
• Have the “Help sheets” feature on;

Steps to reproduce:

1. Using the keyboard navigate to Settings - Privacy features;
2. Open the “Get help” help sheet;
3. Navigate through the content  of the sheet;
4. Tap “ESC” button while the screen reader is still on;

Expected result:

• The sheet is closed and its content is no longer read.

Actual result:

• The sheet is closed, but the content is still read;

┆Issue is synchronized with this Jira Bug ┆Reporter: Valentina Virlics