Consistent sentence case in docs template files (#134412)

Doc/tools/templates/customsourcelink.html

diff --git a/Doc/tools/templates/customsourcelink.html b/Doc/tools/templates/customsourcelink.html
index eb9db9e..43d3a7a 100644
--- a/Doc/tools/templates/customsourcelink.html
+++ b/Doc/tools/templates/customsourcelink.html
@@ -1,11 +1,11 @@
 {%- if show_source and has_source and sourcename %}
   <div role="note" aria-label="source link">
-    <h3>{{ _('This Page') }}</h3>
+    <h3>{{ _('This page') }}</h3>
     <ul class="this-page-menu">
-      <li><a href="{{ pathto('bugs') }}">{% trans %}Report a Bug{% endtrans %}</a></li>
+      <li><a href="{{ pathto('bugs') }}">{% trans %}Report a bug{% endtrans %}</a></li>
       <li>
         <a href="https://github.com/python/cpython/blob/main/Doc/{{ sourcename|replace('.rst.txt', '.rst') }}"
-            rel="nofollow">{{ _('Show Source') }}
+            rel="nofollow">{{ _('Show source') }}
         </a>
       </li>
     </ul>

Doc/tools/templates/download.html

diff --git a/Doc/tools/templates/download.html b/Doc/tools/templates/download.html
index 4645f7d..47a57eb 100644
--- a/Doc/tools/templates/download.html
+++ b/Doc/tools/templates/download.html
@@ -27,7 +27,7 @@
 {%- endblock -%}
 
 {% block body %}
-<h1>{% trans %}Download Python {{ dl_version }} Documentation{% endtrans %}</h1>
+<h1>{% trans %}Download Python {{ dl_version }} documentation{% endtrans %}</h1>
 
 {% if last_updated %}<p><b>{% trans %}Last updated on: {{ last_updated }}.{% endtrans %}</b></p>{% endif %}
 

Doc/tools/templates/indexcontent.html

diff --git a/Doc/tools/templates/indexcontent.html b/Doc/tools/templates/indexcontent.html
index 06a4223..544cc42 100644
--- a/Doc/tools/templates/indexcontent.html
+++ b/Doc/tools/templates/indexcontent.html
@@ -72,7 +72,7 @@
   <table class="contentstable" align="center"><tr>
     <td width="50%">
       <p class="biglink"><a class="biglink" href="{{ pathto("bugs") }}">{% trans %}Reporting issues{% endtrans %}</a></p>
-      <p class="biglink"><a class="biglink" href="https://devguide.python.org/documentation/help-documenting/">{% trans %}Contributing to Docs{% endtrans %}</a></p>
+      <p class="biglink"><a class="biglink" href="https://devguide.python.org/documentation/help-documenting/">{% trans %}Contributing to docs{% endtrans %}</a></p>
       <p class="biglink"><a class="biglink" href="{{ pathto("download") }}">{% trans %}Download the documentation{% endtrans %}</a></p>
     </td><td width="50%">
       <p class="biglink"><a class="biglink" href="{{ pathto("license") }}">{% trans %}History and license of Python{% endtrans %}</a></p>

Doc/tools/templates/indexsidebar.html

diff --git a/Doc/tools/templates/indexsidebar.html b/Doc/tools/templates/indexsidebar.html
index eea29e2..086f156 100644
--- a/Doc/tools/templates/indexsidebar.html
+++ b/Doc/tools/templates/indexsidebar.html
@@ -9,9 +9,9 @@
 <h3>{% trans %}Other resources{% endtrans %}</h3>
 <ul>
   {# XXX: many of these should probably be merged in the main docs #}
-  <li><a href="https://peps.python.org/">{% trans %}PEP Index{% endtrans %}</a></li>
-  <li><a href="https://wiki.python.org/moin/BeginnersGuide">{% trans %}Beginner's Guide{% endtrans %}</a></li>
-  <li><a href="https://wiki.python.org/moin/PythonBooks">{% trans %}Book List{% endtrans %}</a></li>
-  <li><a href="https://www.python.org/doc/av/">{% trans %}Audio/Visual Talks{% endtrans %}</a></li>
-  <li><a href="https://devguide.python.org/">{% trans %}Python Developer’s Guide{% endtrans %}</a></li>
+  <li><a href="https://peps.python.org/">{% trans %}PEP index{% endtrans %}</a></li>
+  <li><a href="https://wiki.python.org/moin/BeginnersGuide">{% trans %}Beginner's guide{% endtrans %}</a></li>
+  <li><a href="https://wiki.python.org/moin/PythonBooks">{% trans %}Book list{% endtrans %}</a></li>
+  <li><a href="https://www.python.org/doc/av/">{% trans %}Audio/visual talks{% endtrans %}</a></li>
+  <li><a href="https://devguide.python.org/">{% trans %}Python developer’s guide{% endtrans %}</a></li>
 </ul>