style: modify hr style.

Author: jaywcjlove

src/styles/markdown.less

@@ -297,12 +297,12 @@ body[data-color-mode*='light'] {
     box-sizing: content-box;
     overflow: hidden;
     background: transparent;
+    border: 0;
     border-bottom: 1px solid var(--color-border-muted);
     height: 0.25em;
     padding: 0;
     margin: 24px 0;
     background-color: var(--color-border-default);
-    border: 0;
   }
   input {
     font: inherit;