cmd/cue: fix link in embed help text

The link was misspelled.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: Ie6bef236009ca80d6815e6a1388f5e78fa2c9682
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1197599
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Paul Jolly <paul@myitcv.io>

cmd/cue/cmd/help.go

@@ -183,7 +183,7 @@ Note: support for embed is experimental, and is enabled via
 CUE_EXPERIMENT=embed.
 
 For more details and discussion, see the proposal linked from
-https://cuelang.org/dicsussion/3264.
+https://cuelang.org/discussion/3264.
 `[1:],
 }