Stop generating the [TOC] in the GN reference docs.

tools/gn/docs/reference.md

 # GN Reference
 
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 *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 the previous build done in that directory. If a command specifies
   --args, it will override the previous arguments stored in the build
@@ skipping 543 matching lines @@
 
   gn ls out/Debug "//base/*" --as=output | xargs ninja -C out/Debug
       Builds all targets in //base and all subdirectories.
 
   gn ls out/Debug //base --all-toolchains
       Lists all variants of the target //base:base (it may be referenced
       in multiple toolchains).
 
 
 ```
-## **gn refs <out_dir> (<label_pattern>|<label>|<file>)* [--all]**
+## **gn refs <out_dir> (<label_pattern>|<label>|<file>|@<response_file>)* [--all]**
 ```
         [--all-toolchains] [--as=...] [--testonly=...] [--type=...]
 
   Finds reverse dependencies (which targets reference something). The
   input is a list containing:
 
    - Target label: The result will be which targets depend on it.
 
    - Config label: The result will be which targets list the given
      config in its "configs" or "public_configs" list.
 
    - Label pattern: The result will be which targets depend on any
      target matching the given pattern. Patterns will not match
      configs. These are not general regular expressions, see
      "gn help label_pattern" for details.
 
    - File name: The result will be which targets list the given file in
      its "inputs", "sources", "public", or "data". Any input
      that does not contain wildcards and does not match a target or a
      config will be treated as a file.
 
+   - Response file: If the input starts with an "@", it will be
+     interpreted as a path to a file containing a list of labels or
+     file names, one per line. This allows us to handle long lists
+     of inputs without worrying about command line limits.
+
 ```
 
 ### **Options**
 
 ```
   --all
       When used without --tree, will recurse and display all unique
       dependencies of the given targets. For example, if the input is
       a target, this will output all targets that depend directly or
       indirectly on the input. If the input is a file, this will output
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 **  --markdown**: write the output in the Markdown format.
 **  --nocolor**: Force non-colored output.
 **  -q**: Quiet mode. Don't print output on success.
 **  --root**: Explicitly specify source root.
 **  --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.
 
 ```