Revert "IPDPProvingSchedule: add service method"

[wjmelements]

Reverts #187
That solution was an alternative to FilOzone/filecoin-services#168 and should not have merged
Currently it breaks the FWSS build.

[wjmelements]

The approach of #187 and FilOzone/filecoin-services#166 was the opposite of FilOzone/filecoin-services#168

Per that approach, the IPDPProvingSchedule is now the PDPListener:

Error: Compiler run failed:
Error (3656): Contract "FilecoinWarmStorageService" should be marked as abstract.
  --> src/FilecoinWarmStorageService.sol:30:1:
   |
30 | contract FilecoinWarmStorageService is
   | ^ (Relevant source part starts here and spans across multiple lines).
Note: Missing implementation:
  --> lib/pdp/src/IPDPProvingSchedule.sol:11:5:
   |
11 |     function service() external view returns (PDPListener);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^