Remove dead leak detector parts that fell out of use in r224703.

llvm-svn: 226867
diff --git a/llvm/lib/IR/LLVMContextImpl.cpp b/llvm/lib/IR/LLVMContextImpl.cpp
index 880e1c1..3370bdb 100644
--- a/llvm/lib/IR/LLVMContextImpl.cpp
+++ b/llvm/lib/IR/LLVMContextImpl.cpp
@@ -97,8 +97,7 @@
     delete I;
 #include "llvm/IR/Metadata.def"
 
-  // Free the constants.  This is important to do here to ensure that they are
-  // freed before the LeakDetector is torn down.
+  // Free the constants.
   std::for_each(ExprConstants.map_begin(), ExprConstants.map_end(),
                 DropFirst());
   std::for_each(ArrayConstants.map_begin(), ArrayConstants.map_end(),