Remove target-os specific gclient dependencies. (#4374)

As we anyway always recommend to set the target_os to android.
Also if you happen to not set the target_os to android it messes up the licenses script output.

CONTRIBUTING.md

@@ -53,7 +53,6 @@ solutions = [
     "safesync_url": "",
   },
 ]
-target_os = ["android"]
 ```
 
  * `cd engine` (Change to the directory in which you put the `.gclient` file.)

DEPS

@@ -346,6 +346,12 @@ deps = {
   'src/third_party/dart/third_party/pkg/yaml':
    Var('chromium_git') + '/external/github.com/dart-lang/yaml' + '@' + Var('dart_yaml_tag'),
 
+  'src/third_party/colorama/src':
+   Var('chromium_git') + '/external/colorama.git' + '@' + '799604a1041e9b3bc5d2789ecbd7e8db2e18e6b8',
+
+  'src/third_party/freetype2':
+   Var('fuchsia_git') + '/third_party/freetype2' + '@' + 'e23a030e9b43c648249477fdf7bf5305d2cc8f59',
+
   'src/third_party/root_certificates':
    Var('chromium_git') + '/external/github.com/dart-lang/root_certificates' + '@' + Var('dart_root_certificates_rev'),
 
@@ -373,17 +379,6 @@ recursedeps = [
   'src/buildtools',
 ]
 
-deps_os = {
-  'android': {
-    'src/third_party/colorama/src':
-     Var('chromium_git') + '/external/colorama.git' + '@' + '799604a1041e9b3bc5d2789ecbd7e8db2e18e6b8',
-
-    'src/third_party/freetype2':
-       Var('fuchsia_git') + '/third_party/freetype2' + '@' + 'e23a030e9b43c648249477fdf7bf5305d2cc8f59',
-  },
-}
-
-
 hooks = [
   {
     # This clobbers when necessary (based on get_landmines.py). It must be the