Is it still valid to use IE=edge,chrome=1?
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" /> serves two purposes.
IE=edgespecifies that IE should run in the highest mode available to that version of IE as opposed to a compatability mode; IE8 can support up to IE8 modes, IE9 can support up to IE9 modes, and so on.
chrome=1specifies that Google Chrome frame should start if the user has it installed
IE=edge flag is still relevant for IE versions 10 and below. IE11 sets this mode as the default.
As for the chrome flag, you can leave it if your users still use Chrome Frame. Despite support and updates for Chrome Frame ending, one can still install and use the final release. If you remove the flag, Chrome Frame will not be activated when installed. For other users,
chrome=1 will do nothing more than consume a few bytes of bandwidth.
I recommend you analyze your audience and see if their browsers prohibit any needed features and then decide. Perhaps it might be better to encourage them to use a more modern, evergreen browser.
Note, the W3C validator will flag
chrome=1 as an error: A meta element with an
http-equiv attribute whose value is X-UA-Compatible must have a content attribute with the value IE=edge.