Bump go.unistack.org/micro/v3 from 3.8.21 to 3.9.0

Bumps [go.unistack.org/micro/v3](https://github.com/unistack-org/micro) from 3.8.21 to 3.9.0.
- [Release notes](https://github.com/unistack-org/micro/releases)
- [Commits](https://github.com/unistack-org/micro/compare/v3.8.21...v3.9.0)

---
updated-dependencies:
- dependency-name: go.unistack.org/micro/v3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/hashicorp/vault/api v1.4.1
 	github.com/imdario/mergo v0.3.12
 	github.com/pierrec/lz4 v2.6.1+incompatible // indirect
-	go.unistack.org/micro/v3 v3.8.21
+	go.unistack.org/micro/v3 v3.9.0
 	golang.org/x/time v0.0.0-20210723032227-1f47c861a9ac // indirect
 	gopkg.in/square/go-jose.v2 v2.6.0 // indirect
 )