Fix nonce uniqueness tests

std::unique consolidates the unique nonces at the start of the `nonces`
vector, but it doesn't modify nonces.size(), so these tests weren't
actually verifying that the nonces were unique. Add a vector::erase
call to shrink the vector.

After upgrading libc++, std::unique is [[nodiscard]] and this bug is
a compiler error.

Bug: 175635923
Test: treehugger
Test: m VtsAidlSharedSecretTargetTest VtsHalKeymasterV4_0TargetTest
Change-Id: I7fd8c40a3920bf3a8988c8065503c78ba36dc742
diff --git a/security/sharedsecret/aidl/vts/functional/SharedSecretAidlTest.cpp b/security/sharedsecret/aidl/vts/functional/SharedSecretAidlTest.cpp
index 51938ba..7599bce 100644
--- a/security/sharedsecret/aidl/vts/functional/SharedSecretAidlTest.cpp
+++ b/security/sharedsecret/aidl/vts/functional/SharedSecretAidlTest.cpp
@@ -164,7 +164,7 @@
     auto nonces = copyNonces(params);
     EXPECT_EQ(sharedSecrets.size(), nonces.size());
     std::sort(nonces.begin(), nonces.end());
-    std::unique(nonces.begin(), nonces.end());
+    nonces.erase(std::unique(nonces.begin(), nonces.end()), nonces.end());
     EXPECT_EQ(sharedSecrets.size(), nonces.size());
 
     auto responses = computeAllSharedSecrets(params);