export command from language/std/date.nu

- change `source` -> `use` in `tests/date`

modules/language/std/date.nu

@@ -1,4 +1,4 @@
-def "date local" [now] {
+export def "date local" [now] {
  insert time {|value|
  let converted = ($now | date to-timezone $value.tz);
 

modules/language/tests/date.nu

@@ -1,5 +1,5 @@
-source ../playground/lib.nu
-source ../std/date.nu
+use ../playground *
+use ../std/date.nu *
 
 def mock-now [] {
  "2021-08-29 03:31:21" | into datetime