pr feedback: simplify the link, and don't scare people with the cla

Author: nedbat

Doc/improvepage.rst

@@ -36,4 +36,4 @@ You have a few options for asking questions or suggesting changes:
   `Docs: problem with "PAGETITLE" <https://github.com/python/cpython/issues/new?title=Docs%3A+problem+with+%22PAGETITLE%22&labels=docs&body=The+page+at+PAGEURL+has+a+problem%3A>`_.
 
 - You can `edit the page on GitHub <https://github.com/python/cpython/blob/main/Doc/PAGESOURCE?plain=1>`_
-  and open a pull request, though you will need to have signed a contributor agreement before it can be merged.
+  to open a pull request and begin the contribution process.

Doc/tools/templates/customsourcelink.html

@@ -16,7 +16,7 @@ <h3>{{ _('This page') }}</h3>
       <li><a href="{{ pathto('bugs') }}">{% trans %}Report a bug{% endtrans %}</a></li>
       <li><a class="improvepage" href="{{ pathto('improvepage') }}?pageurl=https://docs.python.org/3/{{ pagename }}.html&pagesource={{ sourcename|replace('.rst.txt', '.rst') }}">{% trans %}Improve this page{% endtrans %}</a></li>
       <li>
-        <a href="https://github.com/python/cpython/blob/main/Doc/{{ sourcename|replace('.rst.txt', '.rst') }}?plain=1"
+        <a href="https://github.com/python/cpython/blob/main/Doc/{{ pagename }}.rst?plain=1"
             rel="nofollow">{{ _('Show source') }}
         </a>
       </li>