Update roxygen2 to 8.0.0

Change-Id: I08e89fa9421445475c5b5862eba5edc40e8ca323
diff --git a/DESCRIPTION b/DESCRIPTION
index 5c50c3e..0890eaa 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -35,5 +35,5 @@
 Encoding: UTF-8
 LazyData: true
 VignetteBuilder: knitr
-RoxygenNote: 7.3.1
 Roxygen: list(markdown = TRUE)
+Config/roxygen2/version: 8.0.0