debian/patches: Bump client-test timeout to 400s
On various archs, such as armel, a test was timing out:
E.g. https://buildd.debian.org/status/fetch.php?pkg=geary&arch=armel&ver=43.0-1&stamp=1665012932&raw=0
8/8 geary / js-tests TIMEOUT 30.06s killed by signal 15 SIGTERM