BUG: array_api: fix cholesky upper decomp for complex dtypes

[skip travis] [skip azp] [skip circle] [skip cirrus]

Original NumPy Commit: b8257e597a92eed91a2b2227d692f4bcad860f17

Author: lucascolley

array_api_strict/linalg.py

@@ -9,6 +9,7 @@
     complex128
 )
 from ._manipulation_functions import reshape
+from ._elementwise_functions import conj
 from ._array_object import Array
 
 from numpy.core.numeric import normalize_axis_tuple
@@ -53,7 +54,10 @@ def cholesky(x: Array, /, *, upper: bool = False) -> Array:
         raise TypeError('Only floating-point dtypes are allowed in cholesky')
     L = np.linalg.cholesky(x._array)
     if upper:
-        return Array._new(L).mT
+        U = Array._new(L).mT
+        if U.dtype in [complex64, complex128]:
+            U = conj(U)
+        return U
     return Array._new(L)
 
 # Note: cross is the numpy top-level namespace, not np.linalg