Bug 1553458 remove in-content-text-color r=remote-debugging-reviewers,daisuke

Differential Revision: https://phabricator.services.mozilla.com/D40591

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

devtools/client/aboutdebugging-new/src/base.css

@@ -180,7 +180,6 @@ p, h1 {
   font-size: var(--display-10-font-size);
   font-weight: var(--display-10-font-weight);
   line-height: 1.2;
-  color: var(--in-content-text-color);
 }
 
 .main-heading__icon {