style: update `src/style/sidebar.scss` (#670)

src/style/sidebar.scss

@@ -54,7 +54,7 @@
     top: 0;
     right: 0;
     z-index: 998;
-    width: calc(100% - 210px);
+    width: calc(100% - #{$sideBarWidth});
 
     /* fixed-header 属性左上角动画 */
     transition: width var(--pure-transition-duration);