[Documentations] Correct tag in example of connection string to s3

Link: http://osdu.pages.community.opengroup.org/platform/domain-data-mgmt-services/seismic/open-vds/getting-started.html#opening-a-vds

The connection string for s3 could look like this: AccessKeyId=xxx;SecretAccessKey=xxx;SessionToken=xxx;Region=eu-north-1

In this string, 'SecretAccessKey' should be replaced on 'SecretKey', that what function 'createS3OpenOptions' waiting for.