[Moves] Twineedle's poison only procs once

Hello~

According to Bulbapedia, Twineedle has a 20% chance to poison on both of its hits, effectively resulting in a 36% chance of poisoning per use. However, Twineedle appears to only have 20% chance to poison per use, as the proc is only counted once at the end of the move.

Prerequisites (for testing):

- Two players.

- Player A has a very low level Beedrill with Twineedle.

- Player B has a Steel or Poison type that can survive 20 Twineedles.

Steps to Reproduce:

1. Both players fight each other.

2. Player A repeatedly uses Twineedle.

3. Player B repeatedly uses support moves.

4. Count the number of "POISON failed to have any effect" messages.

Current Result:

The proc chance of Twineedle's poison converges toward 20% per use.

Expected Result:

The proc chance of Twineedle's poison should converge toward 36% per use.

Notes:

- Testing it over 5 battles, the total amount of procs was 22 out of 100 uses (Per battles: 6, 4, 5, 2, 5).

- The poison still attempt to proc if the first attack of Twineedle faints the opposing pokemon.