Remove assumeTrue from TetheringTest

Hostside DeviceOwnerTests use JUnit3, which fail on
AssumptionViolatedException instead of skipping the test.

Remove these assumptions in TetheringTest and simply return success
(which matches the workaround in other tests in this module).

Flag: EXEMPT test only

Bug: 418930600
Test: atest DeviceOwnerTest
Change-Id: I1aaa8efd015231b76545056c4d80d7f930132db2
1 file changed