Replace instances of datadeps --> data_deps.

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
@@ skipping 3500 matching lines @@
   See "gn help runtime_deps" for how these are used.
 
 
 ```
 ## **data_deps**: Non-linked dependencies.
 
 ```
   A list of target labels.
 
   Specifies dependencies of a target that are not actually linked into
-  the current target. Such dependencies will built and will be available
+  the current target. Such dependencies will be built and will be available
   at runtime.
 
   This is normally used for things like plugins or helper programs that
   a target needs at runtime.
 
   See also "gn help deps" and "gn help data".
 
 ```
 
 ### **Example**:
@@ skipping 1292 matching lines @@
 **  \--nocolor**: Force non-colored output.
 **  -q**: Quiet mode. Don't print output on success.
 **  \--root**: Explicitly specify source root.
 **  \--runtime-deps-list-file**: Save runtime dependencies for targets in file.
 **  \--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.
 
 ```