Update web project files test with new threshold

Was improved notably in 13.0:

* Environment:                10k
* Environment Version:        13.1.0-pre `59122560c7b`
* Option:                     60s_200rps
* Date:                       2020-05-27
* Run Time:                   59m 47.72s (Start: 01:23:38 UTC, End: 02:23:26 UTC)
* GPT Version:                v1.3.1

NAME                                                     | RPS   | RPS RESULT           | TTFB AVG   | TTFB P90              | REQ STATUS      | RESULT
---------------------------------------------------------|-------|----------------------|------------|-----------------------|-----------------|-------
web_project_files                                        | 20/s  | 17.75/s (>4.80/s)    | 306.75ms   | 406.05ms (<4000ms)    | 100.00% (>95%)  | Passed

Still a touch slower on the larger environments but another issue is raised.