minor #1715 [Site] fix: AppHeader top spacing on mobile (raphael-geffroy)

This PR was merged into the 2.x branch.

Discussion
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[Site] fix: AppHeader top spacing on mobile

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| Issues        | Fix #...
| License       | MIT

The Banner caused the an unwanted space for the opened AppHeader on mobile. This PR tries to fix this by undisplaying the Banner when the AppHeader is open.

Commits
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2a8f02d fix: AppHeader top spacing on mobile

Author: kbond

ux.symfony.com/assets/styles/components/_Banner.scss

@@ -9,6 +9,10 @@
   position: relative;
 }
 
+.Banner:has(+ .App .AppHeader.open) {
+  display: none;
+}
+
 .BannerInner {
   display: flex;
   flex-direction: column;