fix(layout): adjust z-index values (#6365)

Co-authored-by: TJ Egan <tw15egan@gmail.com>
Co-authored-by: Josh Black <josh@josh.black>
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

packages/components/src/globals/scss/_layout.scss

@@ -12,13 +12,13 @@
 /// @group global-layout
 $z-indexes: (
   modal: 9000,
-  overlay: 8000,
-  dropdown: 9100,
-  header: 6000,
+  overlay: 6000,
+  dropdown: 6000,
+  header: 8000,
   footer: 5000,
   hidden: - 1,
   overflowHidden: - 1,
-  floating: 10000,
+  floating: 6000,
 );
 
 /// @access public