Run NetworkStatsManagerTest on R+ devices.

This is not strictly necessary because the NetworkStats code is
only mainlined on T+. But it is useful to run it because it
ensures that any mainline code that uses NetworkStats APIs will
not show up as uncovered in the API coverage dashboard.

The test has not changed much recently and it should not be
difficult to keep it passing on R.

Bug: 229055233
Test: test-only change
Change-Id: Icab9e7c9e6762359cbbc2d69081636e6050573d3
1 file changed