Pin R to 4.3.3.

Installation of rmarkdown fails with the error below. Instead of installing the package, I'll try using an older version of R that may have been used in Fall 2023.

```
Error:
  ! error in pak subprocess
  Caused by error in `verify_extracted_package(filename, pkg_cache)`:
  !
  '/tmp/RtmpBvcQGD/file8842e7b3f5f/base64enc_0.1-3_R_x86_64-pc-linux-gnu.tar.gz'
  is not a valid R package, it is an empty archive.
```

.github/workflows/publish.yml

@@ -27,10 +27,14 @@ jobs:
           # version: 0.9.600
 
       # add software dependencies here
-      - uses: r-lib/actions/setup-r-dependencies@v2
+      - uses: r-lib/actions/setup-r@v2
         with:
-          packages:
-            any::rmarkdown
+          r-version: '4.3.3'
+
+      #- uses: r-lib/actions/setup-r-dependencies@v2
+      #  with:
+      #    packages:
+      #      any::rmarkdown
 
       # publish to GitHub Pages