runtime(tohtml): Update TOhtml to version 9.0v2 (#13050)

runtime(tohtml): Update TOhtml to version 9.0v2 (#13050)

Modified behavior:
  - Change default value of g:html_use_input_for_pc from "fallback" to
    "none". This means with default settings, only the standards-based
    method to make special text unselectable is used. The old method
    relying on unspecified browser behavior for <input> tags is now only
    used if a user specifically enables it.
  - Officially deprecate g:use_xhtml option (in favor of
    g:html_use_xhtml) by issuing a warning message when used.

Bugfixes:
  - Fix issue #8547: LineNr and other special highlight groups did not
    get proper style rules defined when using "hi link".
  - Fix that diff filler was not properly added for deleted lines at the
    end of a buffer.

Other:
  - Refactored function definitions from long lists of strings to use
    :let-heredoc variable assignment instead.
  - Corrected deprecated "." string concatenation operator to ".."
    operator in more places.

Signed-off-by: Christian Brabandt <cb@256bit.org>