change old app links

frontend/.env

@@ -1,5 +1,4 @@
 VITE_TITLE=GenePlexus
 VITE_DESCRIPTION=GenePlexus enables researchers to predict genes similar to an uploaded geneset of interest based on patterns of connectivity in genome-scale molecular interaction networks, with the ability to translate these findings across species.
 VITE_URL=https://geneplexus.net
-VITE_OLD_URL=https://geneplexus-old.net
 VITE_API=https://us-central1-gap-som-dbmi-geneplx-app-p0n.cloudfunctions.net

frontend/src/pages/About.tsx

@@ -132,14 +132,12 @@ const AboutPage = () => {
 
         <p className="center">
           This web app is a re-imagined version of the initial version of
-          GenePlexus, which is still accessible (for a limited time) here:
+          GenePlexus, which has been{" "}
+          <Link to="https://pygeneplexus.readthedocs.io/en/latest/notes/faqs.html">
+            shut down
+          </Link>
+          .
         </p>
-
-        <Button
-          to={import.meta.env.VITE_OLD_URL}
-          text="Old Site"
-          icon={<FaArrowUpRightFromSquare />}
-        />
       </Section>
     </>
   );

frontend/src/pages/Home.tsx

@@ -34,7 +34,7 @@ const HomePage = () => {
         </Flex>
 
         <p className="center">
-          <Link to={import.meta.env.VITE_OLD_URL}>
+          <Link to="https://pygeneplexus.readthedocs.io/en/latest/notes/faqs.html">
             Looking for the old GenePlexus?
           </Link>
         </p>