Fix failing spec

I noticed that one test fails, and it appears that line 31 in long-stack-trace-zone.spec.js should be `expect(log[1].split('--- ').length).toBe(4);`, and not `expect(log[1].split('--- ').length).toBe(3);`, due to the first element being the stack trace constructed by `Zone.Stacktrace.prototype.get`, and one element for each level of nesting in the async chain run via `lstz.run`.