Fix some typos in GN documentation.

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 2139 matching lines @@
     idl("foo") {...
   you will normally want this to expand to something defining a
   source_set or static_library named "foo" (among other things you may
   need). This way, when another target specifies a dependency on
   "foo", the static_library or source_set will be linked.
 
   It is also important that any other targets your template expands to
   have globally unique names, or you will get collisions.
 
   Access the invoking name in your template via the implicit
-  "target_name" variable. This should also be the basis of how other
-  targets that a template expands to to ensure uniquness.
+  "target_name" variable. This should also be the basis for how other
+  targets that a template expands to ensure uniqueness.
 
   A typical example would be a template that defines an action to
   generate some source files, and a source_set to compile that source.
   Your template would name the source_set "target_name" because
   that's what you want external targets to depend on to link your code.
   And you would name the action something like "${target_name}_action"
   to make it unique. The source set would have a dependency on the
   action to make it run.
 
 ```
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 **  \--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.
 
 ```