Fix Chromium support for content property alt text (#6001)
Fix Chromium support for content property alt text (#6001)

It looks like the values for this feature were copied from the parent
feature. Upon a little digging, this feature appears to have landed in
Chromium 77.

https://www.chromestatus.com/features/4550056227110912
chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data