GN docs: update the example of declare_args().

tools/gn/docs/reference.md

 # GN Reference
 
 *This page is automatically generated from* `gn help --markdown all`.
 
 ## **\--args**: Specifies build arguments overrides.
 
 ```
   See "gn help buildargs" for an overview of how build arguments work.
 
   Most operations take a build directory. The build arguments are taken from
@@ skipping 1664 matching lines @@
 
 ### **Example**
 
 ```
   declare_args() {
     enable_teleporter = true
     enable_doom_melon = false
   }
 
   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.
 
 
 ```
 ## **defined**: Returns whether an identifier is defined.
 
 ```
   Returns true if the given argument is defined. This is most useful in
   templates to assert that the caller set things up properly.
@@ skipping 4969 matching lines @@
 **  \--root**: Explicitly specify source root.
 **  \--runtime-deps-list-file**: Save runtime dependencies for targets in file.
 **  \--script-executable**: Set the executable used to execute scripts.
 **  \--threads**: Specify number of worker threads.
 **  \--time**: Outputs a summary of how long everything took.
 **  \--tracelog**: Writes a Chrome-compatible trace log to the given file.
 **  -v**: Verbose logging.
 **  \--version**: Prints the GN version number and exits.
 
 ```