Bump github.com/slack-go/slack from 0.14.0 to 0.15.0

Bumps [github.com/slack-go/slack](https://github.com/slack-go/slack) from 0.14.0 to 0.15.0.
- [Release notes](https://github.com/slack-go/slack/releases)
- [Changelog](https://github.com/slack-go/slack/blob/master/CHANGELOG.md)
- [Commits](slack-go/slack@v0.14.0...v0.15.0)

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

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

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/hashicorp/go-retryablehttp v0.7.7
 	github.com/jonhadfield/githosts-utils v0.0.0-20240729093740-0aeff8e5bf1c
 	github.com/pkg/errors v0.9.1
-	github.com/slack-go/slack v0.14.0
+	github.com/slack-go/slack v0.15.0
 	github.com/stretchr/testify v1.9.0
 	gitlab.com/tozd/go/errors v0.10.0
 	gopkg.in/h2non/gock.v1 v1.1.2

go.sum

@@ -45,8 +45,8 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU5NdKM8=
 github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
-github.com/slack-go/slack v0.14.0 h1:6c0UTfbRnvRssZUsZ2qe0Iu07VAMPjRqOa6oX8ewF4k=
-github.com/slack-go/slack v0.14.0/go.mod h1:hlGi5oXA+Gt+yWTPP0plCdRKmjsDxecdHxYQdlMQKOw=
+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/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=