fix(e2e): correct proxyServerName in node-express-mcp-v2 event proxy

Was copied from node-express but not updated. waitForTransaction keyed
on 'node-express-mcp-v2' would never match events from a proxy
advertising 'node-express', causing all tests to hang.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: betegon

dev-packages/e2e-tests/test-applications/node-express-mcp-v2/start-event-proxy.mjs

@@ -2,5 +2,5 @@ import { startEventProxyServer } from '@sentry-internal/test-utils';
 
 startEventProxyServer({
   port: 3031,
-  proxyServerName: 'node-express',
+  proxyServerName: 'node-express-mcp-v2',
 });