cue: undeprecate Iterator.Label

The necessary functionality for Selector isn't fully there yet.

Keep it hidden, though.

Change-Id: I7d3f65cba99c489f350978153a4bc0bb8d43d327
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/9542
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Paul Jolly <paul@myitcv.org.uk>

cue/types.go

@@ -258,11 +258,12 @@ func (i *Iterator) Selector() Selector {
 	return featureToSel(i.f, i.idx)
 }
 
-// Label reports the label of the value if i iterates over struct fields and
-// "" otherwise.
+// Label reports the label of the value if i iterates over struct fields and ""
+// otherwise.
+//
 //
-// Deprecated: use i.Selector().String(). Note that this will give more accurate
-// string representations.
+// Slated to be deprecated: use i.Selector().String(). Note that this will give
+// more accurate string representations.
 func (i *hiddenIterator) Label() string {
 	if i.f == 0 {
 		return ""