Godot Version
4.7
Question
Can someone help me with this error please 
get_gravity doesn’t take an argument. Remove horizontal_input from it.
Will script still function the same?
Depends what you want achieve, but as @tibaverus said it doesn’t take argument.
what does variable doing in your script?
horizontal_input
I don’t know what you were trying to do, but get_gravity does not take any argument. What did you expect it to do?