Fix character replacements in response shortcuts

[nathanhoad]

This fixes an issue when a character name was a variable in a auto-line response prompt. For example, given this dialogue and assuming player_name was an available variable with a value of "Coco":

Nathan: Here are some responses.
- {{player_name}}: Some response.
- {{player_name}}: Another response.

Previously, this would resolve the prompt text to be something like Some response. Coco but will now correctly resolve to just Some response..