Vendored copy of AWS SDK drifted from forked copy and breaks the build

In the latest release of Amazon SSM Agent, the vendored copy of the AWS SDK in `vendor/` was edited as part of commit https://github.com/aws/amazon-ssm-agent/commit/7425d49001b8fd8089f964bcd2c8a229c1b150a3. The actual fork of the SDK in `extra/`, and referenced in the `replace` directive in `go.mod`, was left untouched. As a result, on `go mod vendor`, the vendored copy loses the bits needed to build the latest release.

Please update the fork of the SDK in `extra/` so that a build succeeds after `go mod vendor`. You may also want to consider a CI check that ensures both copies stay in sync, i.e. a `go mod vendor` produces an empty `git diff`.

Longer term, are there plans to migrate to v2 of the AWS SDK?

Start by reading go.mod and comparing the forked SDK under extra/ with the vendored copy under vendor/. Run go mod vendor, inspect the resulting git diff, and then run the project build to confirm the dependency remains intact. Done means the build succeeds and go mod vendor produces an empty diff; the optional CI check would enforce that condition.

Written by the indexing model from the issue text.