Revert "Correctly detect the presence of gdate"

This reverts commit 4b181df254.

It will result in systems without a GNU date having a literal "N"
in the output.

tests/test_util.fish

@@ -136,7 +136,7 @@ end
 
 # lame timer
 for program in {g,}date
-    if command -q $program
+    if $program --version 1>/dev/null 2>/dev/null
         set milli $program
         set unit ms
         break