Delay changing popover display

Previously would make the popover visible and then reposition
it on the next frame in order to avoid getting called recursively
due to the observer, however this causes the scrollbar to appear
if it wasn't already visible for a single frame which is janky.

This change fixes that.

internal/glance/static/js/popover.js

@@ -98,7 +98,6 @@ function showPopover() {
     }
 
     contentElement.style.maxWidth = contentMaxWidth;
-    containerElement.style.display = "block";
     activeTarget.classList.add("popover-active");
     document.addEventListener("keydown", handleHidePopoverOnEscape);
     window.addEventListener("resize", queueRepositionContainer);
@@ -106,6 +105,8 @@ function showPopover() {
 }
 
 function repositionContainer() {
+    containerElement.style.display = "block";
+
     const targetBounds = activeTarget.dataset.popoverAnchor !== undefined
         ? activeTarget.querySelector(activeTarget.dataset.popoverAnchor).getBoundingClientRect()
         : activeTarget.getBoundingClientRect();