Fix ForumActivityTest
ForumActivityTest#testNestedEntries() has been failing since 17 December.
junit.framework.AssertionFailedError
at junit.framework.Assert.fail(Assert.java:55)
at junit.framework.Assert.assertTrue(Assert.java:22)
at junit.framework.Assert.assertTrue(Assert.java:31)
at org.briarproject.briar.android.forum.ForumActivityTest.testNestedEntries(ForumActivityTest.java:120)