Revert "DEV: Define --footer-nav-height css var (#14008)" (#14327)

Revert “DEV: Define --footer-nav-height css var (#14008)” (#14327)

This reverts commit 3119b881aa6c297e3fdb281188a1d1b9a5fcd349.

diff --git a/app/assets/stylesheets/common/components/footer-nav.scss b/app/assets/stylesheets/common/components/footer-nav.scss
index 194fd4b..71ed2f9 100644
--- a/app/assets/stylesheets/common/components/footer-nav.scss
+++ b/app/assets/stylesheets/common/components/footer-nav.scss
@@ -2,10 +2,7 @@
 // Footer nav bar (displayed in DiscourseHub app and PWAs)
 // --------------------------------------------------
 
-:root {
-  --footer-nav-height: 49px;
-}
-$footer-nav-height: var(--footer-nav-height);
+$footer-nav-height: 49px;
 
 body.footer-nav-visible {
   #main-outlet {

GitHub sha: b90eb0da1488d7c05ffac2561b6a35b70fe02b57

This commit appears in #14327 which was approved by markvanlan. It was merged by pmusaraj.