Update _Pessoas.cs

'Não fiz o Dispose() apropriadamente, estou errado?' :
http://stephenwalther.com/archive/2008/08/20/asp-net-mvc-tip-34-dispose-of-your-datacontext-or-don-t

'Mais sobre o "Using statement"':
http://stackoverflow.com/questions/15538434/do-i-need-to-close-sql-server-connection-with-the-using-keyword