doc/user: fix scrolling (#30992)

Author: nisarhassan12

doc/user/assets/sass/_layout.scss

@@ -345,6 +345,7 @@ table.inline-headings {
     height: 100vh;
     overflow-y: auto;
     font-size: var(--sm);
+    padding-bottom: 8.5rem;
 
     &-top {
         margin-top: var(--pico);