please update pdf.js version

[sylvestre]

Hello from Mozilla,

It would be nice if you could update the pdf.js version shipped here.

4.10.38 is now two years ago and the current version 6.3.289 fixed a lot of issues.

thanks

[solracsf]

@CarlSchwan any specific reason to not target v6.x on #1544 ?

[CarlSchwan]

I'm going to backport it