features: Only change gradient height for feature page.

This gradient works well to display white colored text
on top of it on other pages. So, we only need this change on
features page.

static/styles/portico/landing_page.css

@@ -410,6 +410,10 @@ nav {
 
     z-index: 2;
 
+    .gradients {
+        z-index: -1;
+    }
+
     section {
         max-width: 1440px;
         display: flex;
@@ -2636,10 +2640,6 @@ nav {
     left: 0;
     width: 100%;
     height: 1100px;
-
-    @media (width < 768px) {
-        height: 700px;
-    }
 }
 
 .gradients .gradient.dark-blue {
@@ -4004,6 +4004,10 @@ nav {
             hsl(49, 71%, 68%) 80%
         );
     }
+
+    .features-app .gradients .gradient {
+        height: 700px;
+    }
 }
 
 @media (width <= 375px) {

templates/zerver/features.html

@@ -7,9 +7,9 @@
 {% block portico_content %}
 
 {% include 'zerver/landing_nav.html' %}
-{% include 'zerver/gradients.html' %}
 
 <div class="portico-landing features-app">
+    {% include 'zerver/gradients.html' %}
     <section class="hero">
         <div class="copy">
             <h1>Powerful group chat.</h1>