Fix broken link on how-to-contribute page.

The 'Contribute' link for the Core Project was presenting a 404 error.
Updated the link to point to the correct location of the contribute page
for the Accumulo project.

Gemfile.lock

@@ -49,14 +49,16 @@ GEM
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (5.0.3)
+    rake (13.1.0)
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
     rexml (3.2.6)
     rouge (4.1.2)
     safe_yaml (1.0.5)
-    sass-embedded (1.64.1-x86_64-linux-gnu)
+    sass-embedded (1.69.5)
       google-protobuf (~> 3.23)
+      rake (>= 13.0.0)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
     unicode-display_width (2.4.2)

pages/how-to-contribute.md

@@ -72,7 +72,7 @@ For more information, see the [contributor guide](/contributors-guide/).
 [confluence]: https://cwiki.apache.org/confluence/display/ACCUMULO/Apache+Accumulo+Home
 [contact]: /contact-us/
 [a]: https://github.com/apache/accumulo
-[ac]: https://github.com/apache/accumulo/blob/main/CONTRIBUTING.md
+[ac]: https://github.com/apache/accumulo/blob/main/.github/CONTRIBUTING.md
 [ai]: https://github.com/apache/accumulo/issues
 [w]: https://github.com/apache/accumulo-website
 [wc]: https://github.com/apache/accumulo-website/blob/main/CONTRIBUTING.md