Fix broken 'Improve this page' links using sphinx variable page_source_suffix (#1969)

Author: seisman

doc/_templates/breadcrumbs.html

@@ -5,7 +5,7 @@
 {% block breadcrumbs_aside %}
     <li class="source-link">
         {% if hasdoc(pagename) %}
-            {% if pagename.startswith("api/generated") or suffix == ".ipynb" %}
+            {% if pagename.startswith("api/generated") or page_source_suffix == ".ipynb" %}
                 {% set title = "Suggested improvement for " + pagename %}
                 {% set body = "Please describe what could be improved about this page or the typo/mistake that you found:" %}
                 <a href="https://github.com/{{ github_repo }}/issues/new?title={{ title|urlencode }}&body={{ body|urlencode }}"
@@ -21,7 +21,7 @@
                 <a href="https://github.com/{{ github_repo }}/edit/{{ github_version }}/{{ doc_path }}/{{ example_script }}"
                    class="fa fa-github"> Improve this page</a>
             {% else %}
-                <a href="https://github.com/{{ github_repo }}/edit/{{ github_version }}/{{ doc_path }}/{{ pagename }}{{ suffix }}"
+                <a href="https://github.com/{{ github_repo }}/edit/{{ github_version }}/{{ doc_path }}/{{ pagename }}{{ page_source_suffix }}"
                    class="fa fa-github"> Improve this page</a>
             {% endif %}
         {% endif %}