From 8.5.0.CSV Operator onwards, we should drop support for the 8.3.x DG servers.

This requires customers to ensure that they upgrade from the 8.3.x server to 8.4.x before upgrading to the 8.5.0.CSV Operator. Automatic Operator upgrades wouldn't be an issue, as the user needs to manually change their subscription channel to upgrade to 8.5.0.CSV anyway.

Implementation:
1. Remove the 8.3.1-1 entry from the INFINISPAN_OPERAND_VERSIONS json in the Operator bundle's CSV file

User procedure:
1. Upgrade to the latest 8.4.x.CSV Operator
2. Update all DG clusters to use a 8.4.x server by setting `spec.version` in the Infinispan CR
3. Upgrade to the 8.5.0.CSV Operator
4. (Optional, but recommend) Upgrade DG clusters to use 8.5.x servers