Remove use of NO_MEM_BUFFER (#1330)

Author: Carti-it

NBitcoin/Crypto/HashStream.cs

@@ -310,12 +310,7 @@ public override void WriteByte(byte value)
 
 		public override uint256 GetHash()
 		{
-#if NO_MEM_BUFFER
-			var copy = ms.ToArray();
-			return GetHash(copy, 0, (int)copy.Length);
-#else
 			return GetHash(ms.GetBuffer(), 0, (int)ms.Length);
-#endif
 		}
 
 		protected abstract uint256 GetHash(byte[] data, int offset, int length);

NBitcoin/IBitcoinSerializable.cs

@@ -90,13 +90,9 @@ public static byte[] ToBytes(this IBitcoinSerializable serializable, uint? versi
 
 		public static byte[] ToArrayEfficient(this MemoryStream ms)
 		{
-#if NO_MEM_BUFFER
-			return ms.ToArray();
-#else
 			var bytes = ms.GetBuffer();
 			Array.Resize(ref bytes, (int)ms.Length);
 			return bytes;
-#endif
 		}
 	}
 }