awssqs source - fix README.md to be consistent with secret yaml (#1227)
awssqs source - fix README.md to be consistent with secret yaml (#1227)

README.md used awssqs-source-credentials while awssqs-source.yaml used
aws-credentials.  Just have both use aws-credentials for the secretname
knative-sandbox/eventing-gitlab,knative-sandbox/eventing-awssqs,knative-sandbox/eventing-ceph,knative-sandbox/eventing-couchdb,knative-sandbox/eventing-natss,knative-sandbox/eventing-kafka,knative-sandbox/eventing-camel,knative-sandbox/eventing-ceph,knative-sandbox/eventing-natss,knative-sandbox/eventing-couchdb,knative-sandbox/eventing-awssqs,knative-sandbox/eventing-camel,knative-sandbox/eventing-github,knative-sandbox/eventing-prometheus,knative/eventing-contrib,knative-sandbox/eventing-github,knative-sandbox/eventing-prometheus,knative-sandbox/eventing-gitlab,knative/eventing-contrib,knative-sandbox/eventing-kafka