refine alpha build description for clarity and compatibility

Author: teetow

src/pages/au4.astro

@@ -18,17 +18,14 @@ const { win, mac, lin } = betaReleases;
         <h1>Audacity&nbsp;4 Alpha 1</h1>
         <div class="mt-4">
           <p>
-            The purpose of this alpha build is to test core features of Audacity
-            4. You can help us refine the user experience by chiming in on the
-            forums. If you experience severe issues or crashes, please file an
-            issue on GitHub.
+            The purpose of this alpha build is to test the core features of
+            Audacity 4 on a wide selection of hardware and operating systems.
+          </p>
+          <p>
+            If you experience severe issues or crashes, please file an issue on
+            GitHub (requires a free GitHub account).
           </p>
           <ul class="py-2 list-none">
-            <li class="hyperlink">
-              <a href="https://forum.audacityteam.org/c/au4/64"
-                >Audacity 4 Forum</a
-              >
-            </li>
             <li>
               <a
                 href="https://github.com/audacity/audacity/issues"