refactor(docs-infra): scope TOC styles to the `<aio-toc>` element (#40704)

This commit ensures that all styles for the TOC (which are defined in
`_toc.scss`) only apply to elements inside an `<aio-toc>` element. This
will prevent the styles accidentally taking effect on a different part
of the app.

PR Close #40704

aio/src/styles/2-modules/_toc.scss

@@ -8,6 +8,7 @@
   overflow-x: hidden;
 }
 
+aio-toc {
   .toc-inner {
     @include font-size(13);
     overflow-y: visible;
@@ -189,7 +190,7 @@
   }
 
   // Alternative TOC View for Smaller Screens
-aio-toc.embedded {
+  &.embedded {
     @media (min-width: 801px) {
       display: none;
     }
@@ -207,5 +208,5 @@ aio-toc.embedded {
         }
       }
     }
-
+  }
 }