TST: update array-api-strict-skips.txt with an acosh case

Author: ev-br

array-api-strict-skips.txt

@@ -45,5 +45,6 @@ array_api_tests/test_special_cases.py::test_unary[expm1((real(x_i) is +0 or real
 
 array_api_tests/test_special_cases.py::test_unary[sign((real(x_i) is -0 or real(x_i) == +0) and (imag(x_i) is -0 or imag(x_i) == +0)) -> 0 + 0j]
 array_api_tests/test_special_cases.py::test_unary[tanh(real(x_i) is +infinity and isfinite(imag(x_i)) and imag(x_i) > 0) -> 1 + 0j]
+array_api_tests/test_special_cases.py::test_unary[acosh(real(x_i) is +0 and imag(x_i) is NaN) -> NaN \xb1 \u03c0j/2]
 
 array_api_tests/test_special_cases.py::test_unary[sqrt(real(x_i) is +infinity and isfinite(imag(x_i)) and imag(x_i) > 0) -> +0 + infinity j]