Clean up mobile banner (#13666)

Slight adjustments to the Banner for Mobile

Author: alex-page

polaris.shopify.com/src/components/Frame/Frame.module.scss

@@ -378,7 +378,7 @@ $breakpointNav: $breakpointTablet;
 
   a {
     padding: 0.5rem;
-    border-radius: 9999px;
+    border-radius: 0.5rem;
     color: #00936f;
     background: #d4f5e7;
     display: flex;
@@ -398,6 +398,10 @@ $breakpointNav: $breakpointTablet;
       background: #00936f;
       color: #d4f5e7;
     }
+
+    @media screen and (min-width: $breakpointMobile) {
+      border-radius: 9999px;
+    }
   }
 
   strong {

polaris.shopify.com/src/components/Frame/Frame.tsx

@@ -98,8 +98,7 @@ function Frame({darkMode, children}: Props) {
         <div>
           <a href="https://shopify.dev/beta/next-gen-dev-platform/polaris">
             {icons.Polaris()}
-            <strong>Introducing the new Polaris</strong> - Unified and for the
-            web.{' '}
+            <strong>Introducing Polaris</strong> - Unified and for the web.{' '}
             <span className={styles.ReleaseCandidate}>Release Candidate</span>
             <Icon source={ArrowRightIcon} />
           </a>