Remove context.db from S3 spans: S3 isn't a database

[trentm]

Description

context.db.* was added to the spec for AWS S3 spans by accident. As of spec change #683 any S3 spans created by APM agent instrumentation should not set span.context.db.*.

(My read of the Go and Python APM agent implementations was that they already do not set context.db.* for S3 spans, so I didn't create implementation PRs for them.)

Agent Issues

• [META 696] Remove context.db from S3 spans: S3 isn't a database apm-agent-java#2820
• [META 696] Remove context.db from S3 spans: S3 isn't a database apm-agent-ruby#1313