build(deps): bump github.com/spf13/viper from 1.7.1 to 1.8.0

Bumps [github.com/spf13/viper](https://github.com/spf13/viper) from 1.7.1 to 1.8.0.
- [Release notes](https://github.com/spf13/viper/releases)
- [Commits](spf13/viper@v1.7.1...v1.8.0)

---
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

@@ -18,7 +18,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.11.0
 	github.com/slok/kubewebhook v0.11.0
-	github.com/spf13/viper v1.7.1
+	github.com/spf13/viper v1.8.0
 	github.com/vdemeester/k8s-pkg-credentialprovider v1.18.1-0.20201019120933-f1d16962a4db
 	golang.org/x/crypto v0.0.0-20201002170205-7f63de1d35b0
 	gopkg.in/yaml.v2 v2.4.0