Remove deprecated sphinx-hoverxref extension

- Remove sphinx-hoverxref from root requirements.txt
- Remove hoverxref CSS styling from docs/source/_static/custom.css

The sphinx-hoverxref extension has been deprecated by ReadTheDocs.
Users should enable "Link previews" in the RTD admin dashboard instead.

Co-authored-by: timosachsenberg <5803621+timosachsenberg@users.noreply.github.com>

Author: Copilot

docs/source/_static/custom.css

@@ -40,20 +40,6 @@ div.admonition-video > p.admonition-title::after {
   content: "\f008";
 }
 
-/*terms with tooltips*/
-
-a.hxr-hoverxref {
-  text-decoration: underline;
-  text-decoration-style: dotted;
-  text-decoration-thickness: 2px;
-  text-decoration-color: var(--color-link-underline);
-  border-bottom: none;
-}
-
-a.hxr-hoverxref:hover {
-  text-decoration-color: var(--color-link-underline--hover);
-}
-
 /* second column of API autosummaries should break more and be a bit smaller */
 table.autosummary td:nth-child(2) {
   FONT-WEIGHT: 300;

requirements.txt

@@ -11,7 +11,6 @@ holoviews
 pyviz_comms
 jupyter-server-proxy
 massql
-sphinx-hoverxref
 
 
 pyopenms