fix: Pass all beacons to the relay (#226)

This PR adds all beacon uris to the relay following the advise in
[mev-boost-relay
readme](https://github.com/flashbots/mev-boost-relay#beacon-nodes--cl-clients):
> Relays are strongly advised to run multiple beacon nodes!

---------
Co-authored-by: Gyanendra Mishra <anomaly.the@gmail.com>

main.star

@@ -159,11 +159,13 @@ def run(plan, args={}):
         builder_uri = "http://{0}:{1}".format(
             all_el_client_contexts[-1].ip_addr, all_el_client_contexts[-1].rpc_port_num
         )
-        beacon_uri = [
-            "http://{0}:{1}".format(context.ip_addr, context.http_port_num)
-            for context in all_cl_client_contexts
-        ][-1]
-        beacon_uris = beacon_uri
+        beacon_uris = ",".join(
+            [
+                "http://{0}:{1}".format(context.ip_addr, context.http_port_num)
+                for context in all_cl_client_contexts
+            ]
+        )
+
         first_cl_client = all_cl_client_contexts[0]
         first_client_beacon_name = first_cl_client.beacon_service_name
         mev_flood_module.launch_mev_flood(