minor #1716 [Site] fix: hide IconSearchBox on mobile when AppHeader is open (raphael-geffroy)

This PR was merged into the 2.x branch.

Discussion
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[Site] fix: hide IconSearchBox on mobile when AppHeader is open

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

(Issue 1711 - 3)
When the AppHeader in the icon page on mobile the IconSearchBox is undesirably visible. This PR aims to hide it.

Commits
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c7d5d48 fix: hide IconSearchBox on mobile when AppHeader is open

Author: kbond

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

@@ -6,6 +6,10 @@
 
 }
 
+.AppHeader.open + main .IconSearchBox {
+  position: unset;
+}
+
 .IconSearchBox {
   position: sticky;
   top: 0;