Revert some of "fix: remove hr more simply"

This reverts some of commit feb20e1.

Author: wesleyboar

mkdocs_tacc/tacc_readthedocs/css/tacc-theme/readthedocs-reskin.css

@@ -262,6 +262,11 @@ svg.logo [fill]:not([fill="none"]) {
   content: unset;
 }
 
+/* to hide the <hr> from ReadTheDocs theme markup */
+.rst-content [role="navigation"] hr {
+  display: none;
+}
+
 /* to hide the ≫ from ReadTheDocs theme markup */
 .rst-content [role="navigation"] li::before {
   margin-left: -1.25ch;