Update primitives.mdx

Correct the definition provided for Math.trunc. 
Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/trunc

Author: Sriman97

web/src/pages/concepts/primitives.mdx

@@ -251,7 +251,7 @@ Even though the name says _Not a Number_, it is of type "number"
 - `min` is used to get the smallest of zero or more numbers
 - `sqrt` is used to calculate the square root of the given number
 - `pow` is used to calculate the power base on inputs
-- `trunc` is used to limit the total number of digits to represent the number (method is present on prototype of `Number`)
+- `trunc` is used to returns the integer part of a number by removing any fractional digits (method is present on prototype of `Number`)
 
 ```js copy
 Math.abs(-5));                      // 5