Fix command bot bench-all pallet --pallet= when runtime does not provide requested pallet

[bkontur]

I think it should be possible to fix it, because we have command to list all pallets for runtime:

pallets=($(
  ./target/production/polkadot benchmark pallet --list \
    --chain=./$CHAIN-chain-spec.json |
    tail -n+2 |
    cut -d',' -f1 |
    sort |
    uniq
));

so when runtime does not support a requested pallet, it should just skip and do not fail like this https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/5504933 or https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/5504934