docs: fix canonical links (#19084)

Author: sapphi-red

.vitepress/config.ts

@@ -449,7 +449,7 @@ export default defineConfig({
   transformPageData(pageData) {
     const canonicalUrl = `${ogUrl}/${pageData.relativePath}`
       .replace(/\/index\.md$/, '/')
-      .replace(/\.md$/, '/')
+      .replace(/\.md$/, '')
     pageData.frontmatter.head ??= []
     pageData.frontmatter.head.unshift(
       ['link', { rel: 'canonical', href: canonicalUrl }],