Fix RTD ethical ads placement and styling

Updated sphinx book theme pushes the content down as intended
but local builds without ads have an unwanted scrollbar which must be suppressed

Also tweaks footer styling to avoid slightly misaligned border lines

_static/css/custom.css

@@ -65,6 +65,20 @@ body {
   background-color: var(--pst-color-primary);
 }
 
+/* Remove paragraph bottom margin from footer content */
+.bd-footer-content p {
+  margin-bottom: 0;
+}
+
+/* Prevent unnecessary scrollbar on rtd  */
+.bd-sidebar-primary div#rtd-footer-container:empty {
+  margin: 0;
+}
+
+/* Remove rtd version selector horizontal rule-like border which doesn't line up with the book theme footer */
+.bd-sidebar-primary div#rtd-footer-container .rst-versions.rst-badge .rst-current-version {
+  border-top: 0;
+}
 
 /* Increase the maximum width for large displays. Still limited to prevent very long line length */
 @media (min-width:1200px) {
@@ -77,27 +91,6 @@ body {
   }
 }
 
-/* Styling tweaks for ethical ads. */
-.ethical-sidebar, .ethical-footer {
-  border: 1px solid var(--n8-cool-grey-2-lighter-color);
-  margin-bottom: 2.5rem;
-}
-/* Push down the ethical ads to the bottom of the sidebar, but above the version selector */
-#site-navigation .bd-sidebar__top {
-  min-height: calc(100% - 2em);
-  display: flex;
-  flex-direction: column;
-}
-#ethical-ads-container {
-  margin-top:auto;
-}
-
-/* Override theme rule which was causing a scrollbar within the nav bar when not needed on local builds.
-May need adjusting on rtd for ethical ads*/
-.bd-sidebar-primary .sidebar-primary-items__end {
-  margin-top: inherit;
-}
-
 /* --------------------------------------
   Light theme specific formatting changes
   --------------------------------------- */