Synaptic question re Firefox

[Joe Lowder]

On my Linux Mint system (which is up to date), synaptic
shows Firefox 66.0.3 as the latest version, as shown in
this link image: https://upquick.com/temp/ffversion.jpg

But as you can also see in that link image, when I open
a google document with Firefox, I see the message that says
"This version of Firefox is no longer supported."

So what can I or should I do about that?