fix(docs): remove hardcoded VitePress brand color override

Author: SonyLeo

docs/.vitepress/theme/style.css

@@ -9,7 +9,6 @@ body,
   --rainbow-prev: #009ff7;
   --rainbow-next: #c76dd1;
   --vp-c-brand-soft: rgba(25, 25, 52, 0.1);
-  --vp-c-brand-1: #191919;
   --vp-home-hero-name-color: transparent;
   --vp-home-hero-name-background: -webkit-linear-gradient(120deg, var(--rainbow-prev) 30%, var(--rainbow-next));
   --vp-home-hero-image-background-image: linear-gradient(-45deg, var(--rainbow-prev) 30%, var(--rainbow-next));