Fix merge conflict section in walkthrough

[atoato88]

There is a merge conflict at section of "Adding the framework into our types" in docs/addon/walkthrough/README.md
This PR fix conflict by following current contents of pkg/apis/addons/v1alpha1/dashboard_types.go

[johnsonj]

Thank you!

/assign @justinsb

[justinsb]

Awesome - thanks for fixing @atoato88

/ok-to-test
/approve
/lgtm

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[johnsonj]

@BenTheElder - is there something else we need to do here to kick off Prow?

[BenTheElder]

/test pull-declarative-test

[BenTheElder]

ah we need to enable the trigger plugin https://prow.k8s.io/plugins?repo=kubernetes-sigs%2Fkubebuilder-declarative-pattern

[BenTheElder]

/test pull-declarative-test

[johnsonj]

This is a real failure (but in HEAD, not from this change). #12 should fix.

[johnsonj]

/test pull-declarative-test

[johnsonj]

Thanks for the fix and patience @atoato88