portico: Move open source image above text on mobile.

This moves the image that accompanies the open source section to
be above the text (instead of smushed to the side) on small
windows.

static/styles/landing-page.scss

@@ -3037,6 +3037,20 @@ nav ul li.active::after {
         font-size: 3em;
     }
 
+    .portico-landing.hello .open-source .flex {
+        display: block;
+    }
+
+    .portico-landing.hello .open-source img {
+        display: block;
+        width: 300px;
+        margin: 0 auto;
+    }
+
+    .portico-landing.hello .open-source .il-block {
+        width: 75%
+    }
+
     .portico-landing.integrations .main,
     .main {
         width: auto;