Update workflow

Author: fuodorov

.github/workflows/mdbook.yml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   deploy:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     concurrency:
       group: ${{ github.workflow }}-${{ github.ref }}
     steps:
@@ -17,7 +17,7 @@ jobs:
       - name: Setup mdBook
         uses: peaceiris/actions-mdbook@v2
         with:
-          mdbook-version: '0.4.10'
+          mdbook-version: '0.4.40'
 
       - run: mdbook build
 
@@ -26,4 +26,4 @@ jobs:
         if: ${{ github.ref == 'refs/heads/main' }}
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: ./book
+          publish_dir: ./book