Update discv5 (#3171)

## Issue Addressed

Updates discv5

Pending on
- [x] #3547 
- [x] Alex upgrades his deps

## Proposed Changes

updates discv5 and the enr crate. The only relevant change would be some clear indications of ipv4 usage in lighthouse

## Additional Info

Functionally, this should be equivalent to the prev version.
As draft pending a discv5 release

common/deposit_contract/Cargo.toml

@@ -9,7 +9,7 @@ build = "build.rs"
 [build-dependencies]
 reqwest = { version = "0.11.0", features = ["blocking", "json", "native-tls-vendored"] }
 serde_json = "1.0.58"
-sha2 = "0.9.1"
+sha2 = "0.10"
 hex = "0.4.2"
 
 [dependencies]

common/eth2_network_config/Cargo.toml

@@ -18,4 +18,4 @@ serde_yaml = "0.8.13"
 types = { path = "../../consensus/types"}
 eth2_ssz = "0.4.1"
 eth2_config = { path = "../eth2_config"}
-enr = { version = "0.5.1", features = ["ed25519", "k256"] }
+enr = { version = "0.6.2", features = ["ed25519", "k256"] }