Special case expm1 input dtypes for now

Author: honno

array_api_tests/dtype_helpers.py

@@ -221,6 +221,8 @@ def result_type(*dtypes: DataType):
         func_in_dtypes[name] = dtypes
     elif any("x" in name for name in signature(func).parameters.keys()):
         func_in_dtypes[name] = all_dtypes
+# See https://github.com/data-apis/array-api/pull/413
+func_in_dtypes["expm1"] = float_dtypes
 
 
 func_returns_bool = {