doc/tutorial/basics: change title of section

Change-Id: Id79a09bd9a518a2bf6b08a2f0dd26c3fc2972d1f
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/4700
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/doc/tutorial/basics/0_intro/40_constraints.txt b/doc/tutorial/basics/0_intro/40_constraints.txt
index 80fc450..19ffc03 100644
--- a/doc/tutorial/basics/0_intro/40_constraints.txt
+++ b/doc/tutorial/basics/0_intro/40_constraints.txt
@@ -2,7 +2,7 @@
 cmp stdout expect-stdout-cue
 
 -- frontmatter.toml --
-title = "Duplicates"
+title = "Constraints"
 description = ""
 
 -- text.md --