Bug 1808643 - Adjust minimonth colors for high contrast themes. r=aleca

Differential Revision: https://phabricator.services.mozilla.com/D167995

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

calendar/base/themes/common/widgets/minimonth.css

@@ -77,6 +77,11 @@ calendar-minimonth {
   }
 }
 
+/*
+ * Respect system themes when this setting is enabled and not enabled:
+ * Calendar: Optimize colors for accessibility
+*/
+:not(:root[lwtheme]) calendar-minimonth,
 :root[systemcolors] calendar-minimonth {
   --mmMainBackground: transparent;
   --mmDayColor: WindowText;