Correct brances in input format reference doc.

docs/InputFormatReference.md

 # Input Format Reference
 
 [TOC]
 
 ## Primitive Types
 
 The following primitive types are found within input files:
 
   * String values, which may be represented by enclosing them in
     `'single quotes'` or `"double quotes"`.  By convention, single
@@ skipping 911 matching lines @@
 {
   'sources': [
     'io_posix.cc',
     'io_win.cc',
     'launcher_mac.cc',
     'main.cc',
     'platform_util_linux.cc',
     'platform_util_mac.mm',
   ],
   'sources/': [
-    [['exclude', '_win\\.cc$']],
+    ['exclude', '_win\\.cc$'],
   ],
   'conditions': [
     ['OS!="linux"', {'sources/': [['exclude', '_linux\\.cc$']]}],
     ['OS!="mac"', {'sources/': [['exclude', '_mac\\.cc|mm?$']]}],
     ['OS=="win"', {'sources/': [
-      [['include', '_win\\.cc$']],
-      [['exclude', '_posix\\.cc$']],
+      ['include', '_win\\.cc$'],
+      ['exclude', '_posix\\.cc$'],
     ]}],
   ],
 }
 ```
 
 After the pattern list is applied, `sources` will have the following
 values, depending on the setting of `OS`:
 
   * When `OS` is `linux`: `['io_posix.cc', 'main.cc',
     'platform_util_linux.cc']`
@@ skipping 123 matching lines @@
 
 Given this input, the `sources` list will take on different values based
 on the `OS` variable.
 
   * If `OS` is `"mac"`, `sources` will contain `['common.cc',
     'mac_util.mm', 'posix_main.cc', 'mac_impl.mm']`.
   * If `OS` is `"win"`, `sources` will contain `['common.cc',
     'win_main.cc', 'win_impl.cc']`.
   * If `OS` is any other value such as `"linux"`, `sources` will contain
     `['common.cc', 'posix_main.cc', 'default_impl.cc']`.