Bump github.com/spf13/viper from 1.8.1 to 1.9.0 (#1554)

Bumps [github.com/spf13/viper](https://github.com/spf13/viper) from 1.8.1 to 1.9.0.
- [Release notes](https://github.com/spf13/viper/releases)
- [Commits](spf13/viper@v1.8.1...v1.9.0)

---
updated-dependencies:
- dependency-name: github.com/spf13/viper
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -6,6 +6,6 @@ require (
 	github.com/cpuguy83/go-md2man/v2 v2.0.1
 	github.com/inconshreveable/mousetrap v1.0.0
 	github.com/spf13/pflag v1.0.5
-	github.com/spf13/viper v1.8.1
+	github.com/spf13/viper v1.9.0
 	gopkg.in/yaml.v2 v2.4.0
 )