build(deps): 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]>

Author: dependabot[bot]

go.mod

@@ -6,5 +6,5 @@ require (
 	github.com/aws/aws-sdk-go v1.38.71
 	github.com/pkg/errors v0.9.1
 	github.com/sirupsen/logrus v1.8.1
-	github.com/spf13/viper v1.7.1
+	github.com/spf13/viper v1.8.1
 )