Update CI

Author: jeroen

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

@@ -16,9 +16,8 @@ jobs:
       fail-fast: false
       matrix:
         config:
-          - {os: macos-13,       r: 'release'}
-          - {os: macos-14,       r: 'release'}
-          - {os: macos-15,       r: 'next'}
+          - {os: macos-15,       r: 'release'}
+          - {os: macos-15-intel  r: 'next'}
           - {os: windows-latest, r: 'devel'}
           - {os: windows-latest, r: 'release'}
           - {os: windows-latest, r: '4.3'}