Align toggle sidebar button across all browsers and OSs

app/assets/stylesheets/framework/contextual_sidebar.scss

@@ -322,15 +322,15 @@
   width: $contextual-sidebar-width - 1px;
   transition: width $sidebar-transition-duration;
   position: fixed;
+  height: $toggle-sidebar-height;
   bottom: 0;
-  padding: $gl-padding;
+  padding: 0 $gl-padding;
   background-color: $gray-light;
   border: 0;
   border-top: 1px solid $border-color;
   color: $gl-text-color-secondary;
   display: flex;
   align-items: center;
-  line-height: 1;
 
   svg {
     margin-right: 8px;

app/assets/stylesheets/framework/variables.scss

@@ -10,6 +10,7 @@ $sidebar-breakpoint: 1024px;
 $default-transition-duration: 0.15s;
 $contextual-sidebar-width: 220px;
 $contextual-sidebar-collapsed-width: 50px;
+$toggle-sidebar-height: 48px;
 
 /*
  * Color schema

changelogs/unreleased/toggle-sidebar-alignment.yml

+---
+title: Align toggle sidebar button across all browsers and OSs
+merge_request: 22771
+author:
+type: fixed