Update testing matrix.

Author: davidski

cran-comments.md

@@ -4,15 +4,14 @@ This is a hotfix to address recent breaking changes in `tibble`.
 
 ## Test environments
 
-* local Windows 10 64 install, R 3.5.3
-* local OS X, R 3.6.3
-* Windows Server 2016 (on appveyor), R 3.5
-* Ubuntu 16.04 LTS (on travis-ci)
-  * R-release (both with and without pandoc)
-  * R-devel  (both with and without pandoc)
-* OS X 10.14 (on travis-ci), R-release
-* win-builder (devel and release)
-* local R-devel --enable-long-double=no via docker
+* local Windows 10 64 install, R 4.0.3
+* local OS X, R 4.0.3
+* OS X (via GitHub Actions), R-release
+* win-builder (R-devel and R-release)
+* R-Hub
+  * "devian-gcc-devel-nold" - R-devel --enable-long-double=no
+  * Windows (R-release and R-devel)
+  * Linux (R-release and R-devel)
 
 ## R CMD check results