[Review Apps] Use 2 replicas for the `tiller-deploy` Deployment

What does this MR do?

This will make sure the tiller-deploy Deployment is using 2 replicas so that if one Deployment is evicted because of a memory pressure on its node, the other one can still work and deploy Review Apps in the meantime.

What are the relevant issue numbers?

Closes #55323 (closed).

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• [-] Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer