fixup! book: fix code styling in dark mode

Author: dscho

assets/sass/dark-mode.scss

@@ -84,9 +84,11 @@
             }
 
             /* Book pages: code colors */
-            --book-code-color: #{$fixed-width-font-color};
-            --book-code-bg: #{$no-changes-bg-color};
-            --book-code-border: #{$pre-border};
+            .edition2 {
+                --book-code-color: #{$fixed-width-font-color};
+                --book-code-bg: #{$no-changes-bg-color};
+                --book-code-border: #{$pre-border};
+            }
 
             img {
                 filter: brightness(.6) contrast(1.2);