Description

Update cert manager to 1.15.0:

GatewayAPI support has graduated to Beta. Add the --enable-gateway-api flag to enable the integration. (https://github.com/cert-manager/cert-manager/pull/6961, @ThatsMrTalbot)

Checklist

[x] This PR contains a description of the changes I'm making
[x] I updated the version in Chart.yaml
[x] I updated the changelog with an artifacthub.io/changes annotation in Chart.yaml, check the example in the documentation.
[x] I updated applicable README.md files using pre-commit run
[x] I documented any high-level concepts I'm introducing in docs/
[x] CI is currently green and this is ready for review
[x] I am ready to test changes after they are applied and released