chore(yarn): bump yarn to 4.6.0 & small guide update (#1569)

.yarnrc.yml

@@ -4,4 +4,4 @@ enableGlobalCache: false
 
 nodeLinker: node-modules
 
-yarnPath: .yarn/releases/yarn-4.5.0.cjs
+yarnPath: .yarn/releases/yarn-4.6.0.cjs

guides/MAINTENANCE.md

@@ -41,6 +41,7 @@ Review the security alerts raised by Dependabot [here](https://github.com/parity
 
 ### Yarn Berry version
 - Check if there is a new version of Yarn Berry [here](https://github.com/yarnpkg/berry).
+- To determine which version of Yarn Sidecar is using, we can check the `yarn-X.X.X.cjs` in the [.yarn/releases](https://github.com/paritytech/substrate-api-sidecar/tree/master/.yarn/releases) folder.
 - To update the version, run the command `yarn set version stable`.
 - After upgrading, we can do the usual sanity checks (e.g. `yarn`, `yarn dedupe`).
 

package.json

@@ -87,5 +87,5 @@
     "polkadot",
     "kusama"
   ],
-  "packageManager": "yarn@4.5.0"
+  "packageManager": "yarn@4.6.0"
 }