[3.1.x] Refs #32412 -- Adjusted link from tutorial to reference docs.

The writing code index page is a better location for a newer contributor to
land, than the specific patch guidelines subpage.

Backport of aa29c57 from master

docs/intro/contributing.txt

@@ -19,8 +19,8 @@ Who's this tutorial for?
 
 .. seealso::
 
-    If you are looking for a reference on how to submit patches, see the
-    :doc:`/internals/contributing/writing-code/submitting-patches`
+    If you are looking for a reference on the details of making code
+    contributions, see the :doc:`/internals/contributing/writing-code/index`
     documentation.
 
 For this tutorial, we expect that you have at least a basic understanding of