feat(linter): enable errcheck linter in golangci-lint

Also, bump the linter version to the latest available version.

Signed-off-by: Milos Gajdos <milosthegajdos@gmail.com>

registry/storage/driver/s3-aws/s3_v2_signer.go

@@ -105,6 +105,9 @@ func Sign(req *request.Request) {
 		Time:        req.Time,
 		Credentials: req.Config.Credentials,
 	}
+	// TODO(milosgajdos): figure this out; if Sign returns error which we should check,
+	// we should modify the codepath related to svc.Handlers.Sign.PushBack etc.
+	// nolint:errcheck
 	v2.Sign()
 }