[unittest] Remove TODO comment which caused concern

Remove the second part of the TODO comment that highlighted an issue with
possibly connecting all nodes to the exit of the CFG. This caused concerns
with Jakub Kuderski regarding its feasability, hence we remove it. Such
points are better discussed outside of CFG. If connecting all nodes makes
sense and what the impact is is currently part of an active review discussion.

llvm-svn: 309919

Author: tobiasgrosser

llvm/unittests/IR/DominatorTreeTest.cpp

@@ -454,7 +454,7 @@ TEST(DominatorTree, DeletingEdgesIntroducesUnreachables) {
 // PDT. We also verify this property.
 //
 // TODO: Can we change the PDT definition such that C remains part of the
-//       CFG, at best without loosing the dominance relation D postdom B.
+//       CFG?
 TEST(DominatorTree, DeletingEdgesIntroducesInfiniteLoop) {
   StringRef ModuleString =
       "define void @f() {\n"