remove redundant plotly_build() call

Author: cpsievert

tests/testthat.R

@@ -52,8 +52,7 @@ save_outputs <- function(gg, name) {
       })
     } else {
       tryWhile({
-        p <- plotly_build(p)
-        p$filename=name
+        p$filename <- name
         resp <- plotly_POST(p)
         resp$url
       })