fix(deps): update module github.com/slack-go/slack to v0.9.4 (#186)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

go.mod

@@ -17,7 +17,7 @@ require (
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/rs/xid v1.3.0
 	github.com/rs/zerolog v1.23.0
-	github.com/slack-go/slack v0.9.3
+	github.com/slack-go/slack v0.9.4
 	github.com/spf13/viper v1.8.1
 	github.com/technoweenie/multipartstreamer v1.0.1 // indirect
 	golang.org/x/crypto v0.0.0-20210220033148-5ea612d1eb83 // indirect

go.sum

@@ -307,6 +307,8 @@ github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6Mwd
 github.com/sirupsen/logrus v1.6.0/go.mod h1:7uNnSEd1DgxDLC74fIahvMZmmYsHGZGEOFrfsX/uA88=
 github.com/slack-go/slack v0.9.3 h1:H1UwldF1zWQakjaSymbHMgG3Pg1BiClez/a7JRLdxKc=
 github.com/slack-go/slack v0.9.3/go.mod h1:wWL//kk0ho+FcQXcBTmEafUI5dz4qz5f4mMk8oIkioQ=
+github.com/slack-go/slack v0.9.4 h1:C+FC3zLxLxUTQjDy2RZeMHYon005zsCROiZNWVo+opQ=
+github.com/slack-go/slack v0.9.4/go.mod h1:wWL//kk0ho+FcQXcBTmEafUI5dz4qz5f4mMk8oIkioQ=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d h1:zE9ykElWQ6/NYmHa3jpm/yHnI4xSofP+UP6SpjHcSeM=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d/go.mod h1:OnSkiWE9lh6wB0YB77sQom3nweQdgAjqCqsofrRNTgc=
 github.com/smartystreets/goconvey v1.6.4 h1:fv0U8FUIMPNf1L9lnHLvLhgicrIVChEkdzIKYqbNC9s=