title: Fix flaky TitlePermissionTest::testUserBlock

title: Fix flaky TitlePermissionTest::testUserBlock

The mock timestamp is asserted via $prev, which is set a few lines
up.

The input timestamp is set as 0, which usually passes (if these two
lines execute in the same second), but when the two lines of code
are on opposite sides of a clock second boundary, the test would
fail.

Instead of fixing the setTimestamp() call, remove it in favour of
fixing the 'timestamp' option instead, which was needlessly
being set to one thing and then overwritten by setTimestamp.

Bug: T231166
Change-Id: If6a1e4ec7b91efee0a43e6dd86794f15c5a440b3