Fixes typo in example

a = [ "first", "second", "third", "first" ]
then [ "second" ] is removed, so |a| becomes
[ "first", "third", "first" ]

Change-Id: I5dbbfc05e3ec5e98172b16f529fdc5a33efed83d
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/8480
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Brett Wilson <brettw@chromium.org>

docs/language.md

diff --git a/docs/language.md b/docs/language.md
index 16cb2a4..28bdb7a 100644
--- a/docs/language.md
+++ b/docs/language.md
@@ -116,7 +116,7 @@
 ```
 a = [ "first", "second", "third", "first" ]
 b = a - [ "first" ]  # [ "second", "third" ]
-a -= [ "second" ]  # [ "first", "third", "fourth" ]
+a -= [ "second" ]  # [ "first", "third", "first" ]
 ```
 
 The - operator on a list searches for matches and removes all matching