Fix client reconnection after page refresh (#3117)

## Description:

- Removed all code related to generating a client ID on the client. The
server now assigns the client ID and sends it to the client in lobby
messages.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

w.o.n

src/server/Client.ts

@@ -20,6 +20,5 @@ export class Client {
     public readonly username: string,
     public ws: WebSocket,
     public readonly cosmetics: PlayerCosmetics | undefined,
-    public readonly isRejoin: boolean = false,
   ) {}
 }