fix: Updated Readme with VCs supported by Grandine BN (#527)

This config with mixed Grandine BN <> Lighthouse VC, Grandine BN <> Teku
VC passes:

```
participants:
  - el_type: erigon
    cl_type: grandine
    cl_image: grandine:local
    use_separate_vc: true
    vc_type: lighthouse
    vc_image: sigp/lighthouse:latest
  - el_type: geth
    cl_type: grandine
    cl_image: grandine:local
    use_separate_vc: true
    vc_type: teku
    vc_image: consensys/teku:latest
  - el_type: reth
    cl_type: grandine
    cl_image: grandine:local
    use_separate_vc: true
    vc_type: lighthouse
    vc_image: sigp/lighthouse:latest
    count: 1
network_params:
  deneb_fork_epoch: 1
  min_validator_withdrawability_delay: 1
  shard_committee_period: 1
  num_validator_keys_per_node: 250
launch_additional_services: true
additional_services:
  - dora
  - assertoor
#snooper_enabled: true
disable_peer_scoring: true
assertoor_params:
  image: "ethpandaops/assertoor:master"
  run_stability_check: false
  run_block_proposal_check: false
  tests:
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/stability-check.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/block-proposal-check.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/eoa-transactions-test.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/all-opcodes-test.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/validator-withdrawal-test.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/validator-exit-test.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/validator-slashing-test.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/dencun-opcodes-test.yaml
    - https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/blob-transactions-test.yaml
 ```

README.md

@@ -829,7 +829,7 @@ snooper_enabled: true
 | Teku BN       | ✅            | ❌       | ✅      | ✅          | ✅
 | Lodestar BN   | ✅            | ❌       | ❌      | ✅          | ❌ 
 | Nimbus BN     | ✅            | ❌       | ✅      | ✅          | ✅
-| Grandine BN   | ❌            | ❌       | ❌      | ❌          | ❌ 
+| Grandine BN   | ✅            | ❌       | ✅      | ❌          | ❌
 
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