change to use :not selector

src/client/styles/scss/_wiki.scss

@@ -11,7 +11,11 @@ div.body {
 
 .wiki {
   font-size: 15px;
-  line-height: 1.8em;
+
+  // override line-height except hljs and child of it.
+  :not(.hljs*) {
+    line-height: 1.8em;
+  }
 
   h1,
   h2,
@@ -123,11 +127,6 @@ div.body {
     }
   }
 
-  // in code block
-  pre {
-    line-height: $line-height-base;
-  }
-
   // only inline code blocks
   p code {
     font-family: $font-family-monospace-not-strictly;