test(hotreload): increase caddytest's Client.Timeout (#2431)
## Root cause
`TestHotReload` was failing on
https://github.com/php/frankenphp/actions/runs/25961840516/job/76318473726
(`linux/arm/v7`, dispatched from
https://github.com/php/frankenphp/pull/2430) with:
> context deadline exceeded (Client.Timeout or context cancellation
while reading body)
`caddytest.NewTester` initialises `tester.Client.Timeout = 5s`
(`Default.TestRequestTimeout`). That budget covers the entire roundtrip
including body reads. On an emulated armv7 runner the chain
`os.WriteFile` → e-dant/watcher event → `mercure` publish → SSE chunk
delivery doesn't complete in 5 s, so the streaming `resp.Body.Read` is
killed before the marker `index.php` is seen. The job died at exactly
5.03 s.
## Fix
Set `tester.Client.Timeout = 0` for this test. The test already cancels
the read via `context.WithCancel` once the marker appears in the buffer,
and Go's `-timeout` provides the outer deadline — the 5 s inner cap was
redundant.
The other failing job on that run (`linux/amd64`, e-dant/watcher cmake
build) is unrelated to this PR.
