docs: undocument "platform check" command (#467)

diff --git a/doc/platform.txt b/doc/platform.txt
index d301be0..d352424 100644
--- a/doc/platform.txt
+++ b/doc/platform.txt
@@ -23,7 +23,6 @@
                                         update to the latest <version> if no <plat-spec> is specified
 
     list .............................. List all installed and available platforms
-    check ............................. List platforms which can be updated by `cordova-cli platform update`
     nosave ............................ Prevents saving version of all platforms added to 
                                         config.xml & package.json
 Syntax
diff --git a/doc/readme.md b/doc/readme.md
index 93e9ae2..b3a8164 100644
--- a/doc/readme.md
+++ b/doc/readme.md
@@ -200,7 +200,7 @@
 
 ### Synopsis
 
-Manage cordova platforms - allowing you to add, remove, update, list and check for updates. Running commands to add or remove platforms affects the contents of the project's platforms directory.
+Manage cordova platforms - allowing you to add, remove, update and list platforms. Running commands to add or remove platforms affects the contents of the project's platforms directory.
 
 ### Syntax
 
@@ -209,7 +209,6 @@
     add <platform-spec> [...] {--save | link=<path> } |
     {remove | rm}  platform [...] {--save}|
     {list | ls}  |
-    check |
     save |
     update ]
 ```
@@ -224,7 +223,6 @@
 | update `<platform>` [...] |      | Update specified platforms |
 |     | --save                   | Updates the version specified in `config.xml` |
 | list |                         | List all installed and available platforms |
-| check |                        | List platforms which can be updated via cordova-cli with the command `platform update` |
 
 ### Platform-spec