Scala 2 download pages: link to version-specific notes (#1775)

also remove the unneeded links to the archive old release blog posts

Author: SethTisue

_includes/downloads-scala2.html

@@ -1,8 +1,7 @@
 <p>Released <b>{{page.release_date}}</b>. See <a href="{{ site.baseurl }}/download/all.html">all releases</a>.</p>
 <h3>Release Notes</h3>
-For a summary of important changes, see the <a href="https://github.com/scala/scala/releases">GitHub release notes</a>.
-<br/><small>(Or consult our archive of <a href="{{ site.baseurl }}/blog/releases/">older release
-    notes</a>.)</small>
+For a summary of important changes, see the <a
+  href="https://github.com/scala/scala/releases/tag/v{{page.release_version}}">GitHub release notes</a>.
 
 <div class="install-steps">
   <div class="text-step">

_includes/downloads-scala3.html

@@ -5,8 +5,6 @@
 <h3>Release Notes</h3>
 For a summary of important changes, see the <a
   href="https://github.com/scala/scala3/releases/tag/{{page.release_version}}">GitHub release notes</a>.
-<br /><small>(Or consult our archive of <a href="{{ site.baseurl }}/blog/releases/">older release
-    notes</a>.)</small>
 
 <div class="install-steps">
   <div class="text-step">