cmd/cue/cmd: fix description for --show-optional flag

Closes #292
https://github.com/cuelang/cue/pull/292

GitOrigin-RevId: 81dab99eef165c224badad47731845bb846e3f9f
Change-Id: I9097aa3eb967671c74aa3fe99629c4ed2fb4caf2
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/5040
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/cmd/cue/cmd/eval.go b/cmd/cue/cmd/eval.go
index 0a28c89..e68f614 100644
--- a/cmd/cue/cmd/eval.go
+++ b/cmd/cue/cmd/eval.go
@@ -60,7 +60,7 @@
 		"display hidden attributes")
 
 	cmd.Flags().BoolP(string(flagOptional), "O", false,
-		"display hidden attributes")
+		"display optional attributes")
 
 	cmd.Flags().BoolP(string(flagAttributes), "l", false,
 		"display field attributes")