Release v6.4.0-3 (#1290)

* Code cleaning (#1287)

* Clean migrations and dependencies

* Sync runtime versions

* Use community RPC endpoints

* Patch frontier version (#1286)

* Release `v6.4.0-3`

---------

Co-authored-by: Bear Wang <boundless.forest@outlook.com>

.github/workflows/checks.yml

@@ -123,11 +123,11 @@ jobs:
           [
             {
               chain: darwinia-dev,
-              compare-with: "https://rpc.darwinia-network",
+              compare-with: "https://darwinia-rpc.darwiniacommunitydao.xyz",
             },
             {
               chain: crab-dev,
-              compare-with: "https://crab-rpc.darwinia-network",
+              compare-with: "https://crab-rpc.darwiniacommunitydao.xyz",
             },
             {
               chain: pangoro-dev,