Bug 23050: Fix tab's id to avoid compatibility issues

Bug 23050: Fix tab's id to avoid compatibility issues

MDN says:

  Using characters except ASCII letters, digits, '_', '-' and '.' may
  cause compatibility problems, as they weren't allowed in HTML 4.
  Though this restriction has been lifted in HTML5, an ID should start
  with a letter for compatibility.

https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/id
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>