Fix errorprone build

Fixes:
frameworks/base/tests/net/java/com/android/server/connectivity/tethering/OffloadControllerTest.java:149: error: [JUnit4TestNotRun] Test method will not be run; please add @test annotation
    public void testNoSettingsValueDefaultDisabledDoesNotStart() throws Exception {
                ^
    (see http://errorprone.info/bugpattern/JUnit4TestNotRun)
  Did you mean '@test'?
frameworks/base/tests/net/java/com/android/server/connectivity/tethering/OffloadControllerTest.java:170: error: [JUnit4TestNotRun] Test method will not be run; please add @test annotation
    public void testNoSettingsValueDefaultEnabledDoesStart() throws Exception {
                ^
    (see http://errorprone.info/bugpattern/JUnit4TestNotRun)
  Did you mean '@test'?

Bug: 64489631
Test: m -j RUN_ERROR_PRONE=true javac-check
Merged-In: Ib32489d07778465134bca52c589baddbd78ab129
Change-Id: I41dfdf87529e532df385617fa05c7006a7a14c86