GN docs: update the example of declare_args().

tools/gn/functions.cc

Index: tools/gn/functions.cc
diff --git a/tools/gn/functions.cc b/tools/gn/functions.cc
index 41be19b5206c875f842283aeda5bfb15de00f766..272cd9430bc96d82fef310a8f8ef5600cd3e2725 100644
--- a/tools/gn/functions.cc
+++ b/tools/gn/functions.cc
@@ -429,7 +429,7 @@ Example
   }
 
   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.
 )";