fix: bug with participant counts that lead to more than needed participants (#221)

```json
{
    "participants": [
      {
        "el_client_type": "geth",
        "el_client_image": "ethpandaops/geth:lightclient-devnet-8-edf4ab3",
        "cl_client_type": "lighthouse",
        "cl_client_image": "sigp/lighthouse:deneb",
        "count": 1
      },
      {
        "el_client_type": "geth",
        "el_client_image": "ethpandaops/geth:lightclient-devnet-8-edf4ab3",
        "cl_client_type": "teku",
        "cl_client_image": "consensys/teku:develop",
        "count": 3
      }
    ]
  }
```

Sample input would misbehave before this fix

src/package_io/parse_input.star

@@ -23,6 +23,13 @@ genesis_constants = import_module(
 def parse_input(plan, input_args):
     result = package_io_parser.parse_input(input_args)
 
+    # we do this as the count has already been accounted for by the `package_io_parser`
+    # and we end up sending the same args to `package_io_parser` again when we do eth_network_package.run()
+    # that we have to do as we want to send in MEV participants
+    # this will all be cleaner post merge
+    for participant in result["participants"]:
+        participant["count"] = 1
+
     # add default eth2 input params
     result["mev_type"] = None
     result["mev_params"] = get_default_mev_params()