Merge pull request #2628 from ehuss/update-mdbook

Update mdbook

Author: kinnison

.github/workflows/deploy-docs.yaml

@@ -14,7 +14,7 @@ jobs:
       - name: Install mdbook
         run: |
           mkdir mdbook
-          curl -Lf https://github.com/rust-lang/mdBook/releases/download/v0.4.1/mdbook-v0.4.1-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=./mdbook
+          curl -Lf https://github.com/rust-lang/mdBook/releases/download/v0.4.5/mdbook-v0.4.5-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=./mdbook
           echo "`pwd`/mdbook" >> $GITHUB_PATH
       - name: Build book
         run: cd doc && mdbook build