Revert "Change polling to wait in ServiceWorkerClientTest"

This reverts commit 3c1a14ead86cfea66a0be8c4188da9ea94a652bb.

Reason for revert: this caused test flakiness, see b/443131596

Bug: 37293648
Fixes: 443131596
Change-Id: Ic213aa1c171819d2d49e4899e2d1c675c2486ed8
1 file changed