Update R version for windows in Readme and ci test

Change-Id: Ib9ed7bf63ac4f5f08133bfb67ed4fa4f7ca9289f
diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index 0dee5ab..27ecabb 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -21,7 +21,7 @@
           - os: windows-latest
             python-version: 3.9
           - os: windows-latest
-            r-version: 3.6
+            r-version: release
           - os: ubuntu-latest
             r-version: 3.6
             python-version: 3.9