Update GettingStarted.md if user using zsh filename should be .zshrc

Summary:
Small contribution for MacOS users:

For those users who using zsh with their Mac OS filename to place variables should be different
Closes #10432

Differential Revision: D4078102

Pulled By: lacker

fbshipit-source-id: 6cbfb81a472f37bfda85964e929c99b438348fd8

Author: Kevin Lacker

docs/GettingStarted.md

@@ -138,7 +138,7 @@ The React Native command line interface requires the `ANDROID_HOME` environment
 export ANDROID_HOME=~/Library/Android/sdk
 ```
 
-To avoid doing this every time you open a new Terminal, create (or edit) `~/.bashrc` using your favorite text editor and add the following lines:
+To avoid doing this every time you open a new terminal, add the following lines to your `~/.bashrc` or equivalent config file:
 
 ```
 export ANDROID_HOME=~/Library/Android/sdk