Bug 1546635 - fix about:debugging scrollbar cropped by the viewport;r=ladybenko

Differential Revision: https://phabricator.services.mozilla.com/D28638

--HG--
extra : moz-landing-system : lando

devtools/client/aboutdebugging-new/src/components/App.css

@@ -51,7 +51,7 @@
 
   /* padding will give space for card shadow to appear and
      margin will correct the alignment */
-  margin-inline: calc(var(--card-shadow-blur-radius) * -1);
+  margin-inline-start: calc(var(--card-shadow-blur-radius) * -1);
   padding-inline: var(--card-shadow-blur-radius);
 }