fix: remove deprecated function

[roeeyn]

math.atan2 was deprecated in Lua 5.3 (Reference)

The following functions were deprecated in the mathematical library: atan2, cosh, sinh, tanh, pow, frexp, and ldexp. You can replace math.pow(x,y) with x^y; you can replace math.atan2 with math.atan, which now accepts one or two arguments; ...

local angle = math.atan((Enemy_y - Player_y), (Enemy_x - Player_x))