human_filesize(): avoid Note during pkg installation *

The note was: 'Note: wrong number of arguments to 'floor' at filemanagement.R:258'.

Introduced by 6a3b0ee, where '%>% floor' was replaced by '%>% floor()'. The Note can
be regarded as a bug in R.

Worked around by using '%>% floor(x = .)'

R/filemanagement.R

@@ -257,7 +257,7 @@ human_filesize <- function(x) {
   assert_that(all(x %% 1 == 0 & x >= 0))
   magnitude <-
     log(x, base = 1024) %>%
-    floor() %>%
+    floor(x = .) %>%
     pmin(8)
   unit <- factor(magnitude,
     levels = 0:8,