Hotfix: disable the bootstrap node connectivity check

This used to behave properly before the rebase, but currently
it forces the bootstrap node to exit, because it ends up being
launched with an ENR list telling it to connect to itself.

The root cause will be investigated in a follow-up PR.

beacon_chain/eth2_network.nim

@@ -231,9 +231,10 @@ when networkBackend in [libp2p, libp2pDaemon]:
         node.addKnownPeer bootstrapNode
       await node.start()
 
+      when false:
         await sleepAsync(10.seconds)
-      if bootstrapEnrs.len > 0 and libp2p_successful_dials.value == 0:
-        fatal "Failed to connect to any bootstrap node. Quitting"
+        if libp2p_successful_dials.value == 0:
+          fatal "Failed to connect to any bootstrap node. Quitting", bootstrapEnrs
           quit 1
 
   proc saveConnectionAddressFile*(node: Eth2Node, filename: string) =