🌱 Update to controller-runtime v0.20.4

[embik]

I guess #24 was poor timing on my part, we got controller-runtime v0.20.4 a day or so later. So this PR bumps it to v0.20.4 in multicluster-runtime.

The v0.20.4 changelog is pretty straightforward:

• 🐛 Restmapper: Respect preferred version by @k8s-infra-cherrypick-robot in [release-0.20] 🐛 Restmapper: Respect preferred version controller-runtime#3159
• 🌱 Mention the SkipNameValidation option in the name validation error by @k8s-infra-cherrypick-robot in [release-0.20] 🌱 Mention the SkipNameValidation option in the name validation error controller-runtime#3172
• ✨ Controller: Retain the priority by @k8s-infra-cherrypick-robot in [release-0.20] ✨ Controller: Retain the priority controller-runtime#3173
• ✨Add RELEASE_TAG to tools/setup-envtest to show binary version with setup-envtest version by @k8s-infra-cherrypick-robot in [release-0.20] ✨Add RELEASE_TAG to tools/setup-envtest to show binary version with setup-envtest version controller-runtime#3175
• 🌱 Handlers: Default to LowPriorityWhenUnchanged without a wrapper by @alvaroaleman in [release-0.20] 🌱 Handlers: Default to LowPriorityWhenUnchanged without a wrapper controller-runtime#3179

[sttts]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: e219e06d782481c1f7f195e808ab18a80e17d39f

[k8s-ci-robot]

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