[orca-list] Say all and read by line doesn't give the same result on a web page with Firefox

[Alex ARNAUD <aarnaud hypra fr>]

    Hello,
    
    Tested environment:
    - Debian 9 and 10
    - Orca 3.34 and master
    - Firefox 68 and Nightly
    
    Steps to reproduce:
    1) Open this page: https://www.mozilla.org/en-US/privacy/firefox/
    2) Move on the title "Firefox by default shares data to:"
    3) Press down arrow
    
    Orca reads:
    "Improve performance..."
    
    4) Press up arrow to go back to the title at step 2
    5) Launch say all
    
    Result:
    Orca doesn't read "Improve performance..." and just say "heading
    level 2 ...".
    
    Expected result:
    Orca should read the title both in say all and when read with arrow
    keys
    
    Best regards.