update for C++ README
update for C++ README

imshashank/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,imshashank/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples,awsdocs/aws-doc-sdk-examples