fix(aio): remove heading border (#22401)

PR Close #22401

aio/src/styles/0-base/_typography.scss

@@ -12,16 +12,10 @@ h1 {
   font-size: 24px;
   font-weight: 500;
   margin: 8px 0px;
-}
 
-h1:after {
-  content: "";
-  display: block;
-  height: 1px;
-  width: 40%;
-  margin: 24px 0px 10px;
-  background: $lightgray;
-  clear: both;
+  @media screen and (max-width: 600px) {
+    margin-top: 0;
+  }
 }
 
 h2 {
@@ -60,13 +54,7 @@ h6 {
   clear: both;
 }
 
-h1 {
-  @media screen and (max-width: 600px) {
-    margin: 0;
-  }
-}
-
-h1:after, h2, h3, h4, h5, h6 {
+h2, h3, h4, h5, h6 {
   @media screen and (max-width: 600px) {
     margin: 8px 0;
   }

aio/src/styles/1-layouts/_marketing-layout.scss

@@ -20,10 +20,6 @@
     transform: none;
   }
 
-  h1:after {
-   content: none;
-  }
-
   .hero-title {
     display: inline-block;
     font-size: 28px;