remove the default replicas from validation

[Madhu-1]

Removing the default replica count from the CRD to ensure that we can still allow the user to deploy single controller plugin deployment on the single node cluster.

fixes: #532

Scenario	Expected Replicas	Actual Replicas	Result
Driver CR without replicas, no OperatorConfig	1 (node-count capped)	1	Pass
Driver CR without replicas, OperatorConfig replicas: 2	2 (propagated from OperatorConfig)	2	Pass
Driver CR with explicit replicas: 3	3 (user override wins)	3	Pass

[Madhu-1]

@travisn PTAL all the cases should work , the only issue was with default value in validation