doc: Rework footer

There is likely no need for the footer to be so prominently asking folks
to report issues with a page based on the number of issues that have
been reported in the past year or so.

This change makes the footer less crowded and saves some vertical space.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

doc/_static/css/custom.css

@@ -883,6 +883,11 @@ dark-mode-toggle::part(toggleLabel){
    color: white;
 }
 
+.lastupdated {
+    font-weight: 200;
+    font-size: 0.9rem;
+}
+
 /* Custom search box, including search engine selection */
 
 .search-container {

doc/_templates/footer.html

@@ -6,25 +6,13 @@
   {%- endif %}
 
   {%- if last_updated %}
-  <span class="lastupdated">
-    Last generated on {{ last_updated }}.
-  </span>
-  {%- endif -%}
-</p>
+  <div class="lastupdated">
+    Last generated: {{ last_updated }}.
     {%- set git_last_updated, sha1 = pagename | git_info | default((None, None), true) %}
     {%- if git_last_updated %}
-<div class="admonition tip" data-nosnippet>
-  <p class="admonition-title">
-    Help us keep our technical documentation accurate and up-to-date!
-  </p>
-  <p>
-    The human-authored contents on this page was last updated on {{ git_last_updated }}.
-  </p>
-  <p>
-    If you find any errors on this page, outdated information, or have any other suggestion for
-    improving its contents, please consider
-    <a href="{{ pagename | gh_link_get_open_issue_url(sha1) }}">opening an issue</a>.
-  </p>
-</div>
+    Last source update: {{ git_last_updated }}.
     {%- endif %}
+  </div>
+  {%- endif -%}
+</p>
 {% endblock %}