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/history.go)
- [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>

Author: dependabot[bot]

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/dghubble/sling v1.4.2
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51
 	github.com/samber/lo v1.47.0
-	github.com/slack-go/slack v0.14.0
+	github.com/slack-go/slack v0.15.0
 	github.com/spf13/cobra v1.8.1
 	github.com/spf13/viper v1.19.0
 	github.com/traPtitech/go-traq v0.0.0-20240725071454-97c7b85dc879

go.sum

@@ -50,8 +50,8 @@ github.com/sagikazarmark/slog-shim v0.1.0 h1:diDBnUNK9N/354PgrxMywXnAwEr1QZcOr6g
 github.com/sagikazarmark/slog-shim v0.1.0/go.mod h1:SrcSrq8aKtyuqEI1uvTDTK1arOWRIczQRv+GVI1AkeQ=
 github.com/samber/lo v1.47.0 h1:z7RynLwP5nbyRscyvcD043DWYoOcYRv3mV8lBeqOCLc=
 github.com/samber/lo v1.47.0/go.mod h1:RmDH9Ct32Qy3gduHQuKJ3gW1fMHAnE/fAzQuf6He5cU=
-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/sourcegraph/conc v0.3.0 h1:OQTbbt6P72L20UqAkXXuLOj79LfEanQ+YQFNpLA9ySo=
 github.com/sourcegraph/conc v0.3.0/go.mod h1:Sdozi7LEKbFPqYX2/J+iBAM6HpqSLTASQIKqDmF7Mt0=
 github.com/spf13/afero v1.11.0 h1:WJQKhtpdm3v2IzqG8VMqrr6Rf3UYpEF239Jy9wNepM8=