Upgrade to latest micromark (markdown only) (#18277)

Co-authored-by: fisker Cheung <lionkay@gmail.com>
Co-authored-by: fisker <lionkay@gmail.com>
Co-authored-by: Jed Fox <git@jedfox.com>
Co-authored-by: seiya <20365512+seiyab@users.noreply.github.com>

.github/renovate.json5

@@ -75,9 +75,13 @@
       matchManagers: ["github-actions"],
     },
     {
-      groupName: "docusaurus",
+      groupName: "Docusaurus",
       matchPackageNames: ["@docusaurus/*"],
     },
+    {
+      groupName: "Markdown dependencies",
+      matchPackageNames: ["micromark-*", "mdast-", "remark-", "unified"],
+    },
   ],
   ignoreDeps: [
     // It's a dependency of `remark-parse`, use same version to reduce size