Link "Install vX.YY" button to /install, not the release-specific page.

index.html

@@ -10,7 +10,7 @@
     - label: '<i class="fas fa-info-circle"></i> Learn more'
       url: "about"
     - label: '<i class="fas fa-download"></i> Install v{% include root_stable_version %}'
-      url: "{% include root_stable_version_url %}"
+      url: /install
 feature_row:
   - title: '&Sqrt;-1'
     excerpt: "ROOT enables <i>statistically sound</i> scientific analyses and visualization of large amounts of data: today, more than 1 exabyte (1,000,000,000 gigabyte) are stored in ROOT files. [The Higgs was found with ROOT!](gallery#higgs-plots)"