Less careful about actions versions

Try @main here, will apply in all club repos if this one works.

.github/workflows/deploy_bookdown.yml

@@ -12,7 +12,7 @@ jobs:
     name: Render-Book
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@main
       - uses: r-lib/actions/setup-r@v2
       - uses: r-lib/actions/setup-pandoc@v2
       - uses: r-lib/actions/setup-r-dependencies@v2
@@ -21,7 +21,7 @@ jobs:
 
       - name: Render Book
         run: Rscript -e 'bookdown::render_book("index.Rmd")'
-      - uses: actions/upload-artifact@v2
+      - uses: actions/upload-artifact@main
         with:
           name: _book
           path: _book/