Fix to ensure 100vh min plays nicely w/ Linux+Chrome (#13857)

(cherry picked from commit f72be51aec)

airflow/www/static/css/main.css

@@ -21,6 +21,7 @@ body {
   position: relative;
   padding: 70px 0 100px;
   min-height: 100vh;
+  overflow-y: scroll;
   background-color: #fff;
 }