Update deprecation message for base::ListValue::Reserve().

The current suggestion no longer works as of https://crrev.com/732394.

Bug: 646113
Change-Id: Iae40f884c4258fd3e3017963a85e38c6a82e4d79
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2325710Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792773}

base/values.h

@@ -806,7 +806,8 @@ class BASE_EXPORT ListValue : public Value {
   bool empty() const { return list_.empty(); }
 
   // Reserves storage for at least |n| values.
-  // DEPRECATED, use GetList()::reserve() instead.
+  // DEPRECATED, first construct a base::Value::ListStorage and use
+  // base::Value::ListStorage::reserve() instead.
   void Reserve(size_t n);
 
   // Sets the list item at the given index to be the Value specified by