Update mobile menu width after $medium breakpoint

src/components/site-header/site-header.scss

@@ -9,7 +9,6 @@
   display: flex;
   flex-flow: row;
   place-content: center space-between;
-  position: relative;
   z-index: 99;
 
   @include breakpoint($medium) {
@@ -72,7 +71,7 @@
       z-index: 100;
 
       @include breakpoint($medium) {
-        width: 356px;
+        width: 400px;
       }
     }
   }