doc/tutorials/basic: update hidden.md

Fix typo

Closes #72
https://github.com/cuelang/cue/pull/72

GitOrigin-RevId: 327c31bb72631686adacd6bfd4292937897a2d9e
Change-Id: Ie61bab63df6e46174aa5dcdae51257b065d4fcdf
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2866
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/doc/tutorial/basics/hidden.md b/doc/tutorial/basics/hidden.md
index 02c74a4..2345a6b 100644
--- a/doc/tutorial/basics/hidden.md
+++ b/doc/tutorial/basics/hidden.md
@@ -6,7 +6,7 @@
 
 A non-quoted field name that starts with an underscore (`_`) is not
 emitted from the output.
-To includes fields in the configuration that start with an underscore
+To include fields in the configuration that start with an underscore
 put them in quotes.
 
 Quoted and non-quoted fields share the same namespace unless they start