Update GH actions (#298)

Author: shikokuchuo

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

@@ -25,12 +25,11 @@ jobs:
         config:
           - {os: ubuntu-24.04-arm, r: 'devel', http-user-agent: 'release'}
           - {os: ubuntu-latest,    r: 'release'}
-          - {os: ubuntu-latest,    r: 'oldrel-1'}
           - {os: ubuntu-22.04,     r: 'oldrel-2'}
           - {os: macOS-latest,     r: 'release'}
           - {os: macos-15-intel,   r: 'oldrel-3'}
           - {os: windows-latest,   r: 'release'}
-          - {os: windows-latest,   r: 'oldrel-4'}
+          - {os: windows-latest,   r: 'oldrel-5'}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}