Update the URL fragment to not include "py"

I'm making this change since it's unlikely that folks would've linked to
this specific section, and if they did, this isn't exactly user facing
documentation, so I wouldn't hold this to the same standard.

docs/html/development/architecture/package-finding.rst

@@ -7,7 +7,7 @@ package's functionality is largely exposed through and coordinated by the
 package's ``PackageFinder`` class.
 
 
-.. _index-py-overview:
+.. _index-overview:
 
 Overview
 ********
@@ -89,7 +89,7 @@ case, the ``PackageFinder`` instance is created by the
 ``self_outdated_check.py`` module's ``pip_self_version_check()`` function.
 
 The ``PackageFinder`` class is responsible for doing all of the things listed
-in the :ref:`Overview <index-py-overview>` section like fetching and parsing
+in the :ref:`Overview <index-overview>` section like fetching and parsing
 `PEP 503`_ simple repository HTML pages, evaluating which links in the simple
 repository pages are relevant for each requirement, and further filtering and
 sorting by preference the candidates for install coming from the relevant
@@ -105,7 +105,7 @@ One of ``PackageFinder``'s main top-level methods is
  :ref:`LinkEvaluator <link-evaluator-class>` object to filter out some of
  those links, and then returns a list of ``InstallationCandidates`` (aka
  candidates for install). This corresponds to steps 1-3 of the
- :ref:`Overview <index-py-overview>` above.
+ :ref:`Overview <index-overview>` above.
 2. Constructs a ``CandidateEvaluator`` object and uses that to determine
  the best candidate. It does this by calling the ``CandidateEvaluator``
  class's ``compute_best_candidate()`` method on the return value of