Do not deprecate Memory methods yet

There is a proposal to make this defined behaviour, so remove the
deprecation comment for now.

R=jkummerow@chromium.org

Bug: v8:3770
Change-Id: Iff50ec544473bed844c586ed242bd062e8d530d8
Reviewed-on: https://chromium-review.googlesource.com/1160238Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54882}

src/v8memory.h

@@ -12,8 +12,8 @@ namespace internal {
 
 // Memory provides an interface to 'raw' memory. It encapsulates the casts
 // that typically are needed when incompatible pointer types are used.
-// TODO(all): Avoid using this class, it's undefined behaviour in C++. Use
-// {ReadUnalignedValue} and {WriteUnalignedValue} instead.
+// Note that this class currently relies on undefined behaviour. There is a
+// proposal (http://wg21.link/p0593r2) to make it defined behaviour though.
 class Memory {
  public:
   static uint8_t& uint8_at(Address addr) {