fix(website/page): correct og:image URL

Author: kubosho

src/_layouts/website/page.html

@@ -5,7 +5,7 @@
 {{ super() }}
 <meta name="theme-color" content="#d0ab6b">
 <meta property="og:type" content="website">
-<meta property="og:image" content="http://o2project.github.io/steins-git/images/share/ogp.jpg">
+<meta property="og:image" content="https://o2project.github.io/steins-git/assets/images/share/ogp.jpg">
 <meta property="og:locale" content="ja_JP" />
 <meta name="twitter:card" content="summary_large_image">
 <meta name="twitter:site" content="@kubosho_">