cmd/cue/cmd: fix typo 'filetype' -> 'filetypes'

The usage text of the `--out` and `--outfile` say "run 'cue filetype' for more info". The correct cue subcommand is 'cue filetypes', not 'cue filetype'.

Change-Id: I8ae8aa89fb92a8f8409abcaac788140baabb4f04
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/5800
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/cmd/cue/cmd/flags.go b/cmd/cue/cmd/flags.go
index 131a2be..935a363 100644
--- a/cmd/cue/cmd/flags.go
+++ b/cmd/cue/cmd/flags.go
@@ -51,10 +51,10 @@
 func addOutFlags(f *pflag.FlagSet, allowNonCUE bool) {
 	if allowNonCUE {
 		f.String(string(flagOut), "",
-			`output format (run 'cue filetype' for more info)`)
+			`output format (run 'cue filetypes' for more info)`)
 	}
 	f.StringP(string(flagOutFile), "o", "",
-		`filename or - for stdout with optional file prefix (run 'cue filetype' for more info)`)
+		`filename or - for stdout with optional file prefix (run 'cue filetypes' for more info)`)
 }
 
 func addGlobalFlags(f *pflag.FlagSet) {