[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

src/furo/assets/styles/variables/_spacing.scss

@@ -6,7 +6,8 @@
 @mixin spacing {
   // Header!
   --header-height: calc(
-    var(--sidebar-item-line-height) + 4 * #{var(--sidebar-item-spacing-vertical)}
+    var(--sidebar-item-line-height) + 4 *
+      #{var(--sidebar-item-spacing-vertical)}
   );
   --header-padding: 0.5rem;