Notable changes:
* backend/s3: Automatic validation of `eu-north-1` region
* backend/s3: Support for `credential_process` handling in AWS configuration file
Updated via:
```
go get github.com/aws/aws-sdk-go@v1.16.4
go get github.com/terraform-providers/terraform-provider-aws@v1.52.0
go mod tidy
go mod vendor
```
After a bunch of recent changes/rebasing our vendored dependencies got a
little out of sync w.r.t transitive dependencies through codebases that
are not themselves Go Modules yet.
Brian Flad