“accept” attributes are definitely not supported in Microsoft Edge at this point. I confirmed your behavior as “no go” in edge, but showing up in IE via the […] thing in the upper right of Edge.
The Edge status shows it as “Under Consideration” with just 198 votes at https://wpdev.uservoice.com/forums/257854-microsoft-edge-developer/suggestions/13661175-full-spec-support-for-accept-in-input-type-file .
If you’re interested in implementation of the HTTP Client Hints (aka “accept”) on Edge be sure and vote it up at the URL above.