build(deps): bump github.com/rs/zerolog from 1.20.0 to 1.21.0

Bumps [github.com/rs/zerolog](https://github.com/rs/zerolog) from 1.20.0 to 1.21.0.
- [Release notes](https://github.com/rs/zerolog/releases)
- [Commits](https://github.com/rs/zerolog/compare/v1.20.0...v1.21.0)

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

go.mod

@@ -14,7 +14,7 @@ require (
 	github.com/morikuni/aec v1.0.0
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/opentracing/opentracing-go v1.2.0
-	github.com/rs/zerolog v1.20.0
+	github.com/rs/zerolog v1.21.0
 	github.com/spf13/cobra v1.1.3
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.7.1