Skip warnPartialMatchArgs test on R 3.5

Author: cpsievert

tests/testthat/test-ggplot-warnings.R

@@ -1,4 +1,6 @@
 test_that("ggplotly does not issue partial-argument-match warning", {
+  skip_if_not(getRversion() >= "3.6")
+  
   opts <- options(warnPartialMatchArgs = TRUE)
   on.exit(options(opts), add = TRUE)
   p <- ggplot(data.frame())