Remove unused css variable on the old less file

GitOrigin-RevId: cdb40060540d9173dd11f1653fd8e62b8232dcef

services/web/frontend/stylesheets/core/ol-light-variables.less

@@ -77,8 +77,6 @@
 @toolbar-icon-btn-hover-color: @ol-blue-gray-3;
 @editor-header-logo-background: url(../../../public/img/ol-brand/overleaf-o.svg)
   center / contain no-repeat;
-@editor-header-logo-background-active: url(../../../public/img/ol-brand/overleaf-o-white.svg)
-  center / contain no-repeat;
 @project-name-color: @ol-blue-gray-3;
 @project-rename-link-color: @ol-blue-gray-3;
 @project-rename-link-color-hover: @ol-blue-gray-4;