[RGT][ADT] Remove test assertion that will not be executed.

[probinson]

Summary

Found by the Rotten Green Tests project.

llvm/unittests/ADT/ImmutableSetTest.cpp

TEST_F(ImmutableSetTest, IterLongSetTest) {
   ImmutableSet<long>::Factory f;
   ImmutableSet<long> S = f.getEmptySet();
 
   ImmutableSet<long> S2 = f.add(f.add(f.add(S, 0), 1), 2);
   ImmutableSet<long> S3 = f.add(f.add(f.add(S2, 3), 4), 5);
 
   int i = 0;
   for (ImmutableSet<long>::iterator I = S.begin(), E = S.end(); I != E; ++I) {
-    ASSERT_EQ(i, *I);
     i++;
   }
   ASSERT_EQ(0, i);
 
   i = 0;
   for (ImmutableSet<long>::iterator I = S2.begin(), E = S2.end(); I != E; ++I) {
     ASSERT_EQ(i, *I);
     i++;