fix: add missing semicone

packages/semi-foundation/modal/variables.scss

@@ -72,6 +72,6 @@ $width-modal_footer-border:0; // 模态框 footer 顶部描边宽度
 
 
 //shadow
-$shadow-modal_content: var(--semi-shadow-elevated)
+$shadow-modal_content: var(--semi-shadow-elevated);