Bump github.com/cloudevents/sdk-go/v2 in /slack-webhook (#161)

Bumps [github.com/cloudevents/sdk-go/v2](https://github.com/cloudevents/sdk-go) from 2.14.0 to 2.15.0.
- [Release notes](https://github.com/cloudevents/sdk-go/releases)
- [Commits](cloudevents/sdk-go@v2.14.0...v2.15.0)

---
updated-dependencies:
- dependency-name: github.com/cloudevents/sdk-go/v2
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

slack-webhook/go.mod

@@ -8,7 +8,7 @@ replace github.com/chainguard-dev/platform-examples => ../
 
 require (
 	chainguard.dev/sdk v0.1.1
-	github.com/cloudevents/sdk-go/v2 v2.14.0
+	github.com/cloudevents/sdk-go/v2 v2.15.0
 	github.com/kelseyhightower/envconfig v1.4.0
 	github.com/slack-go/slack v0.12.3
 	k8s.io/api v0.28.4

slack-webhook/go.sum

@@ -1,7 +1,7 @@
 chainguard.dev/sdk v0.1.1 h1:4+cI5oo1uIX7P2SUIWgDWjpwv0/xmr6OQ85wvnFLzBs=
 chainguard.dev/sdk v0.1.1/go.mod h1:KmTz5ff+U3YbgPE5OmAFapKoh8JLg0LIF4ZINoab/JU=
-github.com/cloudevents/sdk-go/v2 v2.14.0 h1:Nrob4FwVgi5L4tV9lhjzZcjYqFVyJzsA56CwPaPfv6s=
-github.com/cloudevents/sdk-go/v2 v2.14.0/go.mod h1:xDmKfzNjM8gBvjaF8ijFjM1VYOVUEeUfapHMUX1T5To=
+github.com/cloudevents/sdk-go/v2 v2.15.0 h1:aKnhLQhyoJXqEECQdOIZnbZ9VupqlidE6hedugDGr+I=
+github.com/cloudevents/sdk-go/v2 v2.15.0/go.mod h1:lL7kSWAE/V8VI4Wh0jbL2v/jvqsm6tjmaQBSvxcv4uE=
 github.com/coreos/go-oidc/v3 v3.7.0 h1:FTdj0uexT4diYIPlF4yoFVI5MRO1r5+SEcIpEw9vC0o=
 github.com/coreos/go-oidc/v3 v3.7.0/go.mod h1:yQzSCqBnK3e6Fs5l+f5i0F8Kwf0zpH9bPEsbY00KanM=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=