Update module github.com/slack-go/slack to v0.16.0

Author: renovate[bot]

go.mod

@@ -7,7 +7,7 @@ toolchain go1.23.3
 require (
 	github.com/DataDog/datadog-go v4.8.3+incompatible
 	github.com/Songmu/flextime v0.1.0
-	github.com/slack-go/slack v0.15.0
+	github.com/slack-go/slack v0.16.0
 	github.com/stretchr/testify v1.9.0
 	github.com/thoas/go-funk v0.9.3
 	k8s.io/api v0.28.4

go.sum

@@ -82,6 +82,8 @@ github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU
 github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
 github.com/slack-go/slack v0.15.0 h1:LE2lj2y9vqqiOf+qIIy0GvEoxgF1N5yLGZffmEZykt0=
 github.com/slack-go/slack v0.15.0/go.mod h1:hlGi5oXA+Gt+yWTPP0plCdRKmjsDxecdHxYQdlMQKOw=
+github.com/slack-go/slack v0.16.0 h1:khp/WCFv+Hb/B/AJaAwvcxKun0hM6grN0bUZ8xG60P8=
+github.com/slack-go/slack v0.16.0/go.mod h1:hlGi5oXA+Gt+yWTPP0plCdRKmjsDxecdHxYQdlMQKOw=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=