Simplify thread_store/GetThreadForUser (#21588)

api4/post_test.go

@@ -3033,7 +3033,7 @@ func TestSetPostUnreadWithoutCollapsedThreads(t *testing.T) {
 
 		threadMembership, appErr := th.App.GetThreadMembershipForUser(th.BasicUser.Id, rootPost1.Id)
 		require.Nil(t, appErr)
-		thread, appErr := th.App.GetThreadForUser(th.BasicTeam.Id, threadMembership, false)
+		thread, appErr := th.App.GetThreadForUser(threadMembership, false)
 		require.Nil(t, appErr)
 		require.Equal(t, int64(2), thread.UnreadMentions)
 		require.Equal(t, int64(3), thread.UnreadReplies)