Fix memory leaks in test_trie

The primary motivation is to make the test suite run clean under
Valgrind so that we don't need to wade through unimportant failures.

test/test_trie.c

@@ -49,6 +49,8 @@ TEST test_trie(void) {
     ASSERT(phrase.start == 2);
     ASSERT(phrase.len == 1);
 
+    phrase_array_destroy(phrases);
+    token_array_destroy(tokens);
     trie_destroy(trie);
 
     PASS();