Fix blocks mixed up between mac, linux and windows in Getting Started…

… doc

Summary:
Fixes #11220
Closes #11229

Differential Revision: D4253097

Pulled By: hramos

fbshipit-source-id: 9821912e25cbf2f3a5a86ea8dc27a85d070af34f

docs/GettingStarted.md

@@ -124,22 +124,20 @@ Run the following command in a Terminal:
 npm install -g react-native-cli
 ```
 
+> If you get an error like `Cannot find module 'npmlog'`, try installing npm directly: `curl -0 -L http://npmjs.org/install.sh | sudo sh`.
+
 <block class="windows linux android" />
 
 ### The React Native CLI
 
 Node.js comes with npm, which lets you install the React Native command line interface.
 
-<block class="mac ios android" />
-
 Run the following command in a Terminal:
 
 ```
 npm install -g react-native-cli
 ```
 
-> If you get a *permission error*, try using sudo: `sudo npm install -g react-native-cli`.
-
 > If you get an error like `Cannot find module 'npmlog'`, try installing npm directly: `curl -0 -L http://npmjs.org/install.sh | sudo sh`.
 
 <block class="mac ios" />