[RFCLAT#6] clatd_test: remove dead test for detect_mtu

Delete the test because it has been moved to netd.
- DetectMtu

Bug: 212345928
Test: atest clatd_test
Change-Id: I9b9d178ae6c2f93699697a46477414ea3c66d9a9
diff --git a/clatd_test.cpp b/clatd_test.cpp
index d6d7e66..8c8eb79 100644
--- a/clatd_test.cpp
+++ b/clatd_test.cpp
@@ -625,11 +625,6 @@
   EXPECT_FALSE(ipv6_prefix_equal(&subnet2, &Global_Clatd_Config.ipv6_local_subnet));
 }
 
-TEST_F(ClatdTest, DetectMtu) {
-  // ::1 with bottom 32 bits set to 1 is still ::1 which routes via lo with mtu of 64KiB
-  ASSERT_EQ(detect_mtu(&in6addr_loopback, htonl(1), 0 /*MARK_UNSET*/), 65536);
-}
-
 TEST_F(ClatdTest, ConfigureTunIpManual) {
   // Create an interface for configure_tun_ip to configure and bring up.
   TunInterface v4Iface;