[ci] remove Visual Studio 2017 CI job for R-package (#5079)

* Update r_package.yml

* replace R 4.1 with R 3.6 for VS 2019 build

.github/workflows/r_package.yml

@@ -84,19 +84,12 @@ jobs:
             toolchain: MSYS
             r_version: 4.1
             build_type: cmake
-          # Visual Studio 2017
-          - os: windows-2016
-            task: r-package
-            compiler: MSVC
-            toolchain: MSVC
-            r_version: 3.6
-            build_type: cmake
           # Visual Studio 2019
           - os: windows-2019
             task: r-package
             compiler: MSVC
             toolchain: MSVC
-            r_version: 4.1
+            r_version: 3.6
             build_type: cmake
           # Visual Studio 2022
           - os: windows-2022