update smallvec (#2152)

## Issue Addressed

`cargo audit` is failing because of a potential for an overflow in the version of `smallvec` we're using

## Proposed Changes

Update to the latest version of `smallvec`, which has the fix


Co-authored-by: realbigsean <seananderson33@gmail.com>

beacon_node/beacon_chain/Cargo.toml

@@ -21,7 +21,7 @@ merkle_proof = { path = "../../consensus/merkle_proof" }
 store = { path = "../store" }
 parking_lot = "0.11.0"
 lazy_static = "1.4.0"
-smallvec = "1.4.2"
+smallvec = "1.6.1"
 lighthouse_metrics = { path = "../../common/lighthouse_metrics" }
 log = "0.4.11"
 operation_pool = { path = "../operation_pool" }

beacon_node/eth2_libp2p/Cargo.toml

@@ -23,7 +23,7 @@ dirs = "3.0.1"
 fnv = "1.0.7"
 lazy_static = "1.4.0"
 lighthouse_metrics = { path = "../../common/lighthouse_metrics" }
-smallvec = "1.4.2"
+smallvec = "1.6.1"
 tokio-io-timeout = "0.5.0"
 lru = "0.6.0"
 parking_lot = "0.11.0"

beacon_node/network/Cargo.toml

@@ -32,7 +32,7 @@ futures = "0.3.7"
 error-chain = "0.12.4"
 tokio = { version = "0.3.2", features = ["full"] }
 parking_lot = "0.11.0"
-smallvec = "1.4.2"
+smallvec = "1.6.1"
 rand = "0.7.3"
 fnv = "1.0.7"
 rlp = "0.4.6"