Indicate that abs() of the minimum integer value for signed dtypes is undefined (#250)

* Indicate that abs() of the minimum integer value for signed dtypes is undefined

* Move the abs(smallest signed integer) text into a note

* Update copy

* Remove blank line

* Update copy

"smallest" is ambiguous, as could mean `0` or the minimum value (e.g., `-128` for `int8`).

* Fix missing article

Co-authored-by: Athan <kgryte@gmail.com>

Author: asmeurer

spec/API_specification/elementwise_functions.md

@@ -24,6 +24,10 @@ A conforming implementation of the array API standard must provide and support t
 
 Calculates the absolute value for each element `x_i` of the input array `x` (i.e., the element-wise result has the same magnitude as the respective element in `x` but has positive sign).
 
+```{note}
+For signed integer data types, the absolute value of the minimum representable integer is implementation-dependent.
+```
+
 #### Special Cases
 
 For floating-point operands,