Remove `service` instance variable from integrations contollers

What does this MR do?

After !62011 (merged) was merged, integration views no longer use the @service instance variable. Thus we can remove it from the relevant controllers.

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No changes

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Conformity

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Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

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Related to #329759 (closed)