build(deps): bump github.com/spf13/viper from 1.8.1 to 1.9.0

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>

go.mod

@@ -73,7 +73,7 @@ require (
 	github.com/sourcegraph/go-diff v0.6.1
 	github.com/spf13/cobra v1.2.1
 	github.com/spf13/pflag v1.0.5
-	github.com/spf13/viper v1.8.1
+	github.com/spf13/viper v1.9.0
 	github.com/ssgreg/nlreturn/v2 v2.2.1
 	github.com/stretchr/testify v1.7.0
 	github.com/tdakkota/asciicheck v0.0.0-20200416200610-e657995f937b