sizeof(Node0) also needs to be < kBytesPerKey

Also remove vestigial comment.

CC #9

ConflictSet.cpp

@@ -273,9 +273,8 @@ static_assert(sizeof(Node256) < kMinChildrenNode256 * kBytesPerKey);
 static_assert(sizeof(Node48) < kMinChildrenNode48 * kBytesPerKey);
 static_assert(sizeof(Node16) < kMinChildrenNode16 * kBytesPerKey);
 static_assert(sizeof(Node4) < kMinChildrenNode4 * kBytesPerKey);
+static_assert(sizeof(Node0) < kBytesPerKey);
 
-// Bounds memory usage in free list, but does not account for memory for partial
-// keys.
 template <class T, int64_t kMemoryBound = (1 << 20),
           int64_t kMaxIndividual = (1 << 10)>
 struct BoundedFreeListAllocator {