Avoid as.nanotime for ancient {nanotime}

Author: MichaelChirico

inst/tests/other.Rraw

@@ -718,13 +718,13 @@ if (loaded[["nanotime"]]) {
   test(27, na.omit(DT), DT[c(1,3)])
 
   # rbind with vectors with class attributes #5309
-  x = data.table(a=1L, b=as.nanotime(0))
+  x = data.table(a=1L, b=nanotime(0))
   y = data.table(a=2L, b=NA)
-  test(27.01, rbind(x,y), data.table(a = c(1L, 2L), b=as.nanotime(c(0, NA))))
-  test(27.02, rbind(y,x), data.table(a = c(2L, 1L), b=as.nanotime(c(NA, 0))))
+  test(27.01, rbind(x,y), data.table(a = c(1L, 2L), b=nanotime(c(0, NA))))
+  test(27.02, rbind(y,x), data.table(a = c(2L, 1L), b=nanotime(c(NA, 0))))
   y[, b := NULL]
-  test(27.03, rbind(x,y, fill = TRUE), data.table(a = c(1L, 2L), b=as.nanotime(c(0, NA))))
-  test(27.04, rbind(y,x, fill = TRUE), data.table(a = c(2L, 1L), b=as.nanotime(c(NA, 0))))
+  test(27.03, rbind(x,y, fill = TRUE), data.table(a = c(1L, 2L), b=nanotime(c(0, NA))))
+  test(27.04, rbind(y,x, fill = TRUE), data.table(a = c(2L, 1L), b=nanotime(c(NA, 0))))
 
   # Was 1.91-1.94 in nafill.Rraw, #6139
   l = list(a=nanotime(c(1:2,NA,4:5)), b=nanotime(c(NA,2L,NA,4L,NA)))
@@ -784,7 +784,7 @@ if (loaded[["dplyr"]]) {
 
 if (loaded[["nanotime"]]) {
   # respect dec=',' for nanotime, related to #6446, corresponding to tests 2281.*
-  test(31, fwrite(data.table(as.nanotime(.POSIXct(0))), dec=',', sep=';'), output="1970-01-01T00:00:00,000000000Z")
+  test(31, fwrite(data.table(nanotime(.POSIXct(0))), dec=',', sep=';'), output="1970-01-01T00:00:00,000000000Z")
 }
 
 # tables() with large environment #6607