Don't know if anyone else answered this question in a "deal with it now" manner, or simply how to disable it from ever appearing.
I can't help with preventing it from happening, but the solution to make it go away if you turn it on by accident:
In Edge, it appears to be tab specific.
right at the top of the page, under the address bar, you will see a bar. Towards the right of the page, you will see a play/pause button and an "x".
click the "x" to close out the live read aloud.
lol.
I didn't want to leave my laptop on mute for eternity.
:)
James