Earlier today, Microsoft updated the Canary branch of Chromium-based Edge to v79.0.300.0. The update brought general bug fixes and improvements to the web browser.
In the new update, Microsoft also made some UI changes and the company seems to be ditching the rounded corners. First spotted by a Reddit user, Microsoft has removed the rounded corners from the Omnibox as well as from the in-private browsing indicator. The change comes after some Edge Canary users sent feedback to Microsoft stating that the rounded corners didn’t look good on Microsoft Edge.
The new update should download automatically. You can manually check for updates by heading to the About Microsoft Edge section.