GN docs: update the example of declare_args().

tools/gn/docs/reference.md

Index: tools/gn/docs/reference.md
diff --git a/tools/gn/docs/reference.md b/tools/gn/docs/reference.md
index 7e85b104afb29935f66b6e260888659ccf0565c1..ff151d8e2c57ddaf5e7aec2ad71f3fefb45e3a3d 100644
--- a/tools/gn/docs/reference.md
+++ b/tools/gn/docs/reference.md
@@ -1682,7 +1682,7 @@
   }
 
   If you want to override the (default disabled) Doom Melon:
-    gn --args="enable_doom_melon=true enable_teleporter=false"
+    gn --args="enable_doom_melon=true enable_teleporter=true"
   This also sets the teleporter, but it's already defaulted to on so it will
   have no effect.