fix(opentelemetry-operator): remove default resource values

[Starefossen]

Having default values makes it impossible to remove the CPU limits since the default values will always be merged in with anything set by the user. Setting CPU limits are considered an anti pattern ref. https://komodor.com/learn/kubernetes-cpu-limits-throttling/

[TylerHelmuth]

@Starefossen if you're not using this chart as a subchart you can do:

resources:
  limits:
    cpu: null
    memory: 512Mi

But we can follow the same pattern/reasoning as #745

[github-actions]

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