Skip all fft signature tests for dask

Author: asmeurer

dask-skips.txt

@@ -1,5 +1,17 @@
 # FFT isn't conformant
 array_api_tests/test_fft.py
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.fft]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.ifft]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.fftn]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.ifftn]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.rfft]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.irfft]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.rfftn]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.irfftn]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.hfft]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.ihfft]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.fftfreq]
+array_api_tests/test_signatures.py::test_extension_func_signature[fft.rfftfreq]
 
 # slow and not implemented in dask
 array_api_tests/test_linalg.py::test_matrix_power