GHA: Check from R 4.0

Author: HenrikBengtsson

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

@@ -27,7 +27,7 @@ jobs:
           - {os: ubuntu-latest,  r: 'oldrel'   }
           - {os: ubuntu-latest,  r: 'oldrel-1' }
           - {os: ubuntu-latest,  r: 'oldrel-2' }
-          - {os: ubuntu-latest,  r: '3.6'      }
+          - {os: ubuntu-latest,  r: '4.0'      }
           - {os: ubuntu-latest,  r: 'release'  , language: ko,    label: ko    }
           - {os: ubuntu-latest,  r: 'release'  , language: zh_CN, label: zh_CN }
           - {os: ubuntu-latest,  r: 'release'  , language: zh_TW, label: zh_TW }