fix(external-dns): fix external-dns rbac

[dennismaxjung]

Description
Adds EndpointSlices to rbac for use with kubernetes 1.33 (https://kubernetes.io/blog/2025/04/24/endpoints-deprecation/) (kubernetes-sigs/external-dns#5573)
⚒️ Fixes #

⚙️ Type of change

• ⚙️ Feature/App addition
• 🪛 Bugfix
• ⚠️ Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 🔃 Refactor of current code
• 📜 Documentation Changes

🧪 How Has This Been Tested?

I've tested it on my local cluster by manual expanding the rbac with endpointslices

📃 Notes:

✔️ Checklist:

• ⚖️ My code follows the style guidelines of this project
• 👀 I have performed a self-review of my own code
• #️⃣ I have commented my code, particularly in hard-to-understand areas
• 📄 I have made changes to the documentation
• 🧪 I have added tests to this description that prove my fix is effective or that my feature works
• ⬆️ I increased versions for any altered app according to semantic versioning
• I made sure the title starts with feat(chart-name):, fix(chart-name):, chore(chart-name):, docs(chart-name): or fix(docs):

➕ App addition

If this PR is an app addition please make sure you have done the following.

• 🖼️ I have added an icon in the Chart's root directory called icon.png

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[truecharts-admin]

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