Make h3 smaller than h2

Summary:
After moving to docusaurus v2, our h3 tags are bigger than the h2 tags.
Removing our custom css fixes this, so doing that to get closer to the default theme.

Reviewed By: mweststrate

Differential Revision: D21283840

fbshipit-source-id: ceaf7488b90bbb90a463037d9e1dfcca1d694366

website/static/css/custom.css

@@ -3,6 +3,8 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
+ *
+ * @format
  */
 
 :root {
@@ -222,21 +224,6 @@ h6 {
   align-self: center;
 }
 
-.col h3 {
-  font-size: 28px;
-  font-weight: 300;
-  margin-bottom: 20px;
-  margin-top: 0;
-}
-
-.col h4 {
-  margin: 0;
-  font-weight: 500;
-  font-size: 0.8em;
-  opacity: 0.7;
-  text-transform: uppercase;
-}
-
 .col p {
   opacity: 0.7;
 }