update mongodb homebrew code example

Example 1: brew services start mongodb

//Starts Mongdb server @ mongodb://127.0.0.1:27017/
brew services start mongodb-community@4.2

//Stops Mongdb server @ mongodb://127.0.0.1:27017/
brew services stop mongodb-community@4.2

//mongo
mongo - starts the mongo client

Example 2: brew mongo start

brew services start mongodb-community@4.4