Remove excess margin rule from calendar popover

This negative margin adjusted the popover to go under the sidebar.

The React rewrite changed where sidebar is in the dom so the margin adjustment is no longer necessary.

Affects issues:
- Fixed #3932
- Fixed #3668

Plan/react/dashboard/src/style/style.css

@@ -1328,18 +1328,6 @@ than 3 events in one day on the sessions calendar.
     transform: translateX(0);
 }
 
-/*
-When the sidebar is visible, it offsets the popovers by its width.
- The rules below fix that by applying a negative margin.
- */
-body .fc-popover {
-    margin-left: -14rem;
-}
-
-body.sidebar-hidden .fc-popover {
-    margin-left: 0 !important;
-}
-
 body.sidebar-hidden .navbar-nav {
     display: none;
 }