fix: fix a mistake in the websocket context acceptance mechanism (#6006)

Author: bsod90

packages/cubejs-server-core/src/core/server.ts

@@ -446,7 +446,7 @@ export class CubejsServerCore {
         basePath: this.options.basePath,
         checkAuthMiddleware: this.options.checkAuthMiddleware,
         contextRejectionMiddleware: this.contextRejectionMiddleware.bind(this),
-        wsContextAcceptor: this.contextAcceptor.shouldAcceptWs,
+        wsContextAcceptor: this.contextAcceptor.shouldAcceptWs.bind(this.contextAcceptor),
         checkAuth: this.options.checkAuth,
         queryRewrite:
           this.options.queryRewrite || this.options.queryTransformer,