removed useless doctest for AC4 in Sudoku because AC4's tests are already present in test_csp.py

Author: dmeoli

csp.py

@@ -673,36 +673,6 @@ class Sudoku(CSP):
     >>> h = Sudoku(harder1)
     >>> backtracking_search(h, select_unassigned_variable=mrv, inference=forward_checking) is not None
     True
-
-    >>> e = Sudoku(easy1)
-    >>> e.display(e.infer_assignment())
-    . . 3 | . 2 . | 6 . .
-    9 . . | 3 . 5 | . . 1
-    . . 1 | 8 . 6 | 4 . .
-    ------+-------+------
-    . . 8 | 1 . 2 | 9 . .
-    7 . . | . . . | . . 8
-    . . 6 | 7 . 8 | 2 . .
-    ------+-------+------
-    . . 2 | 6 . 9 | 5 . .
-    8 . . | 2 . 3 | . . 9
-    . . 5 | . 1 . | 3 . .
-    >>> AC4(e); e.display(e.infer_assignment())
-    True
-    4 8 3 | 9 2 1 | 6 5 7
-    9 6 7 | 3 4 5 | 8 2 1
-    2 5 1 | 8 7 6 | 4 9 3
-    ------+-------+------
-    5 4 8 | 1 3 2 | 9 7 6
-    7 2 9 | 5 6 4 | 1 3 8
-    1 3 6 | 7 9 8 | 2 4 5
-    ------+-------+------
-    3 7 2 | 6 8 9 | 5 1 4
-    8 1 4 | 2 5 3 | 7 6 9
-    6 9 5 | 4 1 7 | 3 8 2
-    >>> h = Sudoku(harder1)
-    >>> backtracking_search(h, select_unassigned_variable=mrv, inference=forward_checking) is not None
-    True
     """
 
     R3 = _R3