Metrics emission from pd is broken

[conorsch]

We recently lost pd metrics emission. As of v0.65.0, polling a running pd instance for metrics shows nothing:

❯ curl -s http://localhost:9000/metrics

whereas cometbft still works fine:

❯ curl -s http://localhost:26660/metrics | head -n 3
# HELP cometbft_abci_connection_method_timing_seconds Timing for each ABCI method.
# TYPE cometbft_abci_connection_method_timing_seconds histogram
cometbft_abci_connection_method_timing_seconds_bucket{chain_id="penumbra-testnet-deimos",method="begin_block",type="sync",le="0.0001"} 0

We can see this drop-off on preview, starting ~2d ago:

which corresponds with the merge of #3745. Notably we also touched metrics in #3747, but those changes were cometbft-specific, and do not appear to have broken emission.

[conorsch]

Fixed via #3801, confirmed by checking preview metrics post-deploy.