chore: remove fixed theme color

web/index.html

@@ -5,8 +5,6 @@
     <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png" />
     <link rel="icon" type="image/webp" href="/logo.webp" />
     <link rel="manifest" href="/site.webmanifest" />
-    <meta name="theme-color" media="(prefers-color-scheme: light)" content="#f4f4f5" />
-    <meta name="theme-color" media="(prefers-color-scheme: dark)" content="#18181b" />
     <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no" />
     <!-- memos.metadata.head -->
     <title>Memos</title>