style: change custom css style

Author: DangoRepo

.vitepress/theme/vars.css

@@ -50,8 +50,8 @@
     --glb-customtable-content-bg-lv3: #17171f;
     --glb-customtable-content-bg-lv4: #15151a;
 
-    --demoblock-c-bg: #2a2a30;
-    --demoblock-c-bg-html: #24242a;
+    --demoblock-c-bg: #2a2a2a;
+    --demoblock-c-bg-html: #242424;
     --demoblock-c-bg-preview: #202020;
 
     --usagetable-c-bg-correct: #2d4a28f5;