Add supported values for 'peeringCidrRange' on 'google_apigee_instance' resource

[modular-magician]

Add supported values for peeringCidrRange on google_apigee_instance resource. Supported values from the documentation: https://cloud.google.com/apigee/docs/reference/apis/apigee/rest/v1/organizations.instances#CidrRange

Added test. Since Evaluation organizations support only 22 and 23, I tested 22.

fixes hashicorp/terraform-provider-google#10112

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Release Note Template for Downstream PRs (will be copied)

Google Apigee Instance: Add supported values for 'peeringCidrRange'.

Derived from GoogleCloudPlatform/magic-modules#5472