Class for thrown errors has changed, doc is now outdated

[SpencerBrown]

The base class used to be Aws::EC2::Errors::ServiceError, somewhere recently it changed to just Aws::EC2::Errors. I've adapted my code but the documentation needs to be fixed, see

http://docs.aws.amazon.com/sdkforruby/api/Aws/EC2/Errors.html

and there are probably other places too.

[trevorrowe]

Closing as a duplicate of aws/aws-sdk-ruby#710