tests/cpydiff: Remove core_function_unpacking now that it succeeds.

Commit 1e70fda6 fixes this difference.

tests/cpydiff/core_function_unpacking.py

-"""
-categories: Core,Functions
-description: Unpacking function arguments in non-last position isn't detected as an error
-cause: Unknown
-workaround: The syntax below is invalid, never use it in applications.
-"""
-print(*(1, 2), 3)