[Black Jack]: ✏️ Updates to instructions. (#3660)

* ✏️ Update instructions.md

if we already have an ace, the upcoming ace's value should be 1
https://en.wikipedia.org/wiki/Blackjack?lang=en#Rules_of_play_at_casinos
[...] and aces count as either 1 or 11 according to the player's choice.

* ✏️ Update instructions.md

The instructions on the exercise [black_jack](https://exercism.org/tracks/python/exercises/black-jack) might be improved.
It could be better to refer to the value of the upcoming ace instead of the value of those in hand since this doesn't apply if we have two aces in hand.

Current instructions:
 `Hint: if we already have an ace in hand then its value would be 11.`

Proposed instructions:
 `Hint: if we already have an ace in hand, then the value for the upcoming ace would be 1.`

Sources: "[...] and aces count as either 1 or 11 according to the player's choice." from [Wikipedia](https://en.wikipedia.org/wiki/Blackjack?lang=en#Rules_of_play_at_casinos).

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Co-authored-by: Federico Ponce de Leon <fpleon@intrasoft.com.ar>

exercises/concept/black-jack/.docs/instructions.md

@@ -67,7 +67,7 @@ Define the `value_of_ace(<card_one>, <card_two>)` function with parameters `card
 Your function will have to decide if the upcoming ace will get a value of 1 or a value of 11, and return that value.
 Remember: the value of the hand with the ace needs to be as high as possible _without_ going over 21.
 
-**Hint**: if we already have an ace in hand then its value would be 11.
+**Hint**: if we already have an ace in hand, then the value for the upcoming ace would be 1.
 
 ```python
 >>> value_of_ace('6', 'K')