doc: make Stability labels not sticky in Stability index

PR-URL: #58291
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Dario Piotrowicz <dario.piotrowicz@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ulises Gascón <ulisesgascongonzalez@gmail.com>
Reviewed-By: Tierney Cyren <hello@bnb.im>

Author: LiviaMedeiros

doc/api_assets/style.css

@@ -299,6 +299,10 @@ li.picker-header a span {
   position: static;
 }
 
+#api-section-documentation .api_stability {
+  position: static;
+}
+
 .api_stability * {
   color: var(--white) !important;
 }