Removed duplication borders in the post list

boards/static/css/md/base_page.css

@@ -58,6 +58,18 b' body {'
     border-bottom: 1px solid #777;
 }
 
+.post + .post {
+    border-top: none;
+}
+
+.dead_post + .dead_post {
+    border-top: none;
+}
+
+.archive_post + .archive_post {
+    border-top: none;
+}
+
 .metadata {
     padding-top: 5px;
     margin-top: 10px;