Reduce cpu request for pods according to their utilization

What does this MR do?

Reduce default CPU request for some review app pods that have not been utilizing their requested cpu, following discussion in #34102 (comment 231600353)

• minio - reducing from 100m to 5m
• nginx-ingress/controller - reducing from 150m to 100m
• unicorn/unicorn - reducing from 600m to 400m

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team