Bump dependencies to fix CI (rust-lang#1610)

Author: camelid

src/doc/rustc-dev-guide/.github/workflows/ci.yml

@@ -16,8 +16,8 @@ jobs:
     env:
       MDBOOK_VERSION: 0.4.21
       MDBOOK_LINKCHECK_VERSION: 0.7.6
-      MDBOOK_MERMAID_VERSION: 0.11.2
-      MDBOOK_TOC_VERSION: 0.9.0
+      MDBOOK_MERMAID_VERSION: 0.12.6
+      MDBOOK_TOC_VERSION: 0.11.2
       DEPLOY_DIR: book/html
       BASE_SHA: ${{ github.event.pull_request.base.sha }}
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}