Replace documentation link with links to clients

In research we found that developers orientate themselves around the
API clients rather than the documentation.

We should get them to the client documentation as quickly as possible.

We currently link to the API documentation in three places:
- API integration page
- global footer
- template ‘API info’ page

For the first two this commit:
- removes the link to the documentation
- adds links to each of the 5 clients

For the last one it just removes the link entirely.

app/templates/views/api-keys.html

@@ -58,11 +58,19 @@
     {{ api_key(current_service.id, "Service ID", thing="service ID") }}
   </div>
 
-  <h2 class="heading-small">Documentation</h2>
-  <p>
-    See the
-    <a href="{{ url_for('.documentation') }}">
-    API documentation</a> for clients and specfications.
-  </p>
+  <h2 class="heading-small">API clients</h2>
+  <ul class="list list-bullet">
+    {% for name, url in [
+      ('Java', 'https://github.com/alphagov/notifications-java-client'),
+      ('Node JS', 'https://github.com/alphagov/notifications-node-client'),
+      ('PHP', 'https://github.com/alphagov/notifications-php-client'),
+      ('Python', 'https://github.com/alphagov/notifications-python-client'),
+      ('Ruby', 'https://github.com/alphagov/notifications-ruby-client')
+    ] %}
+    <li>
+      <a href="{{ url }}">{{ name }}</a>
+    </li>
+    {% endfor %}
+  </ul>
 
 {% endblock %}