Improve math.abs annotation

This brings it in line with math.max, and max.min. This change allows the type inference to correctly infer the returned type if math.abs is passed an integer as an argument.

Author: C3pa

meta/template/math.lua

@@ -15,8 +15,9 @@
 math = {}
 
 ---#DES 'math.abs'
----@param x number
----@return number
+---@generic Number: number
+---@param x Number
+---@return Number
 ---@nodiscard
 function math.abs(x) end