style: remove old relays from readme (#353)

Removes kiln and ropsten from the list of testnets that are supported for testing

README.md

@@ -182,22 +182,6 @@ Run mev-boost pointed at our [Goerli Relay](https://builder-relay-goerli.flashbo
  ./mev-boost -goerli -relay-check -relays https://0xafa4c6985aa049fb79dd37010438cfebeb0f2bd42b115b89dd678dab0670c1de38da0c4e9138c9290a398ecd9a0b3110@builder-relay-goerli.flashbots.net
 ```
 
-### Ropsten testnet
-
-Run mev-boost pointed at our [Ropsten Relay](https://builder-relay-ropsten.flashbots.net/):
-
-```
- ./mev-boost -ropsten -relay-check -relays https://0xb124d80a00b80815397b4e7f1f05377ccc83aeeceb6be87963ba3649f1e6efa32ca870a88845917ec3f26a8e2aa25c77@builder-relay-ropsten.flashbots.net
-```
-
-### Kiln testnet
-
-Run mev-boost pointed at our [Kiln Relay](https://builder-relay-kiln.flashbots.net):
-
-```bash
-./mev-boost -kiln -relay-check -relays https://0xb5246e299aeb782fbc7c91b41b3284245b1ed5206134b0028b81dfb974e5900616c67847c2354479934fc4bb75519ee1@builder-relay-kiln.flashbots.net
-```
-
 ### Sepolia testnet
 
 Run mev-boost pointed at our [Sepolia Relay](https://builder-relay-sepolia.flashbots.net/):