fix: update Carbon Ads styles

Author: clampr

src/css/custom.css

@@ -30,8 +30,9 @@
 
 .carbon-ads {
   min-height: 102px;
-  padding: 1.5rem 1.5rem 0;
-  font-size: 0.8125rem;
+  margin-top: 1.5rem;
+  padding: 1rem;
+  font-size: 0.75rem;
   line-height: 1.4;
   text-align: left;
   background-color: #f8f9fa;