Upgrade: Bump github.com/spf13/viper from 1.7.1 to 1.8.1

Bumps [github.com/spf13/viper](https://github.com/spf13/viper) from 1.7.1 to 1.8.1.
- [Release notes](https://github.com/spf13/viper/releases)
- [Commits](spf13/viper@v1.7.1...v1.8.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

go.mod

@@ -16,20 +16,13 @@ require (
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/onsi/ginkgo v1.11.0 // indirect
 	github.com/onsi/gomega v1.8.1 // indirect
-	github.com/pelletier/go-toml v1.6.0 // indirect
 	github.com/pkg/errors v0.9.1
 	github.com/rubenv/sql-migrate v0.0.0-20200212082348-64f95ea68aa3
-	github.com/spf13/afero v1.2.2 // indirect
-	github.com/spf13/cast v1.3.1 // indirect
 	github.com/spf13/cobra v0.0.7
-	github.com/spf13/jwalterweatherman v1.1.0 // indirect
-	github.com/spf13/pflag v1.0.5 // indirect
-	github.com/spf13/viper v1.7.1
+	github.com/spf13/viper v1.8.1
 	github.com/valyala/fasthttp v1.17.0
 	github.com/volatiletech/inflect v0.0.0-20170731032912-e7201282ae8d // indirect
 	github.com/volatiletech/null v8.0.0+incompatible
 	github.com/volatiletech/sqlboiler v3.7.1+incompatible
 	golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9
-	gopkg.in/ini.v1 v1.52.0 // indirect
-	gopkg.in/yaml.v2 v2.2.8 // indirect
 )