Update dependency uwsgi to v2.0.21

This MR contains the following updates:

Package	Update	Change
uwsgi (changelog)	patch	==2.0.19.1 -> ==2.0.21

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templates/admin/base_site.html

@@ -32,6 +32,11 @@
             font-size: 5vw;
             text-align: center;
         }
+
+        /* Fix delete button height in admin interface */
+        .submit-row a.deletelink, .delete-confirmation form .cancel-link {
+            height: auto!important;
+        }
         </style>
     {% endcompress %}
 {% endblock %}