fix semantics to specify a ghost (#3702)

Author: demeesterdev

exercises/concept/ghost-gobble-arcade-game/.docs/instructions.md

@@ -8,7 +8,7 @@ You have four rules to implement, all related to the game states.
 
 ## 1. Define if Pac-Man eats a ghost
 
-Define the `eat_ghost()` function that takes two parameters (_if Pac-Man has a power pellet active_ and _if Pac-Man is touching a ghost_) and returns a Boolean value if Pac-Man is able to eat the ghost.
+Define the `eat_ghost()` function that takes two parameters (_if Pac-Man has a power pellet active_ and _if Pac-Man is touching a ghost_) and returns a Boolean value if Pac-Man is able to eat a ghost.
  The function should return `True` only if Pac-Man has a power pellet active and is touching a ghost.
 
 ```python

exercises/concept/ghost-gobble-arcade-game/.meta/exemplar.py

@@ -6,7 +6,7 @@ def eat_ghost(power_pellet_active, touching_ghost):
 
     :param power_pellet_active: bool - does the player have an active power pellet?
     :param touching_ghost: bool - is the player touching a ghost?
-    :return: bool - can the ghost be eaten?
+    :return: bool - can a ghost be eaten?
     """
 
     return power_pellet_active and touching_ghost

exercises/concept/ghost-gobble-arcade-game/arcade_game.py

@@ -6,7 +6,7 @@ def eat_ghost(power_pellet_active, touching_ghost):
 
     :param power_pellet_active: bool - does the player have an active power pellet?
     :param touching_ghost: bool - is the player touching a ghost?
-    :return: bool - can the ghost be eaten?
+    :return: bool - can a ghost be eaten?
     """
 
     pass