Create DesktopTasksLimiter even if there is no task limit

because DesktopTasksLimiter is responsible for reporting minimization
events to DesktopRepository too.
We need it even if there is no task limit to make sure the state of
DesktopRepository gets updated correctly.

Bug: 397323419
Test: WMShellUnitTests
Flag: EXEMPT - bug fix
Change-Id: If3c25d10b6cc44b58363ff7de1d8334bdf8faa27