ci: trim R-CMD-check matrix to 4 jobs

Author: shamykyzer

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

@@ -16,17 +16,9 @@ jobs:
       matrix:
         include:
           - { os: "ubuntu-latest", python: "3.13", r: "release", backend: "venv" }
-          - { os: "ubuntu-latest", python: "3.13", r: "release", backend: "conda" }
-
           - { os: "windows-latest", python: "3.13", r: "release", backend: "venv" }
-          - { os: "windows-latest", python: "3.13", r: "release", backend: "conda" }
-
           - { os: "macOS-latest", python: "3.13", r: "release", backend: "venv" }
-          - { os: "macOS-latest", python: "3.13", r: "release", backend: "conda" }
-
           - { os: "ubuntu-latest", python: "3.10", r: "oldrel-1", backend: "venv" }
-          - { os: "ubuntu-latest", python: "3.10", r: "oldrel-2", backend: "venv" }
-          - { os: "ubuntu-latest", python: "3.10", r: "oldrel-3", backend: "venv" }
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}