chore(deps-dev): Bump @types/ws from 7.4.1 to 7.4.7 (#177)

Bumps [@types/ws](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/ws) from 7.4.1 to 7.4.7.
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package.json

@@ -54,7 +54,7 @@
     "@relaycorp/ws-mock": "^2.4.1",
     "@types/jest": "^26.0.24",
     "@types/verror": "^1.10.5",
-    "@types/ws": "^7.4.1",
+    "@types/ws": "^7.4.7",
     "axios-mock-adapter": "^1.19.0",
     "del-cli": "^4.0.1",
     "jest": "^27.0.6",

src/lib/PoWebClient.ts

@@ -296,7 +296,7 @@ export class PoWebClient implements GSCClient {
       ws.once('message', async (message) => {
         let challenge: HandshakeChallenge;
         try {
-          challenge = HandshakeChallenge.deserialize(bufferToArray(message));
+          challenge = HandshakeChallenge.deserialize(bufferToArray(message as Buffer));
         } catch (error) {
           ws.close(WebSocketCode.CANNOT_ACCEPT, 'Malformed handshake challenge');
           reject(