temporarily remove testing with R-devel on Windows (GHA can not install it - non-cmdstanr related issue)

Author: rok-cesnovar

.github/workflows/R-CMD-check.yaml

@@ -25,7 +25,7 @@ jobs:
         config:
           - {os: macOS-latest, r: 'devel'}
           - {os: macOS-latest, r: 'release'}
-          - {os: windows-latest, r: 'devel'}
+          # - {os: windows-latest, r: 'devel'}
           - {os: windows-latest, r: 'release'}
           - {os: windows-latest, r: 'oldrel'}
           - {os: ubuntu-20.04, r: 'devel'}