remove version limitation on decorator

[qbisi]

as far as i have tested on my firedrake develop enviroment built with nix, decorator 5.1.1 works well, and no test fails cause of newer version of decorator.

since old version of decorator conflict with ipykernel which is built with decorator 5.1.1.

can you test remove the version limitation of decorator on other platform.

Update:
these 4 pyop2 tests failed with decorator 5.1.1

FAILED tests/pyop2/test_api.py::TestDatAPI::test_dat_illegal_set - AttributeError: 'str' object has no attribute 'total_size'
FAILED tests/pyop2/test_api.py::TestDatAPI::test_dat_illegal_name[1] - Failed: DID NOT RAISE <class 'pyop2.exceptions.NameTypeError'>
FAILED tests/pyop2/test_api.py::TestDatAPI::test_dat_illegal_name[2] - Failed: DID NOT RAISE <class 'pyop2.exceptions.NameTypeError'>
FAILED tests/pyop2/test_api.py::TestDatAPI::test_dat_illegal_name[dset2] - Failed: DID NOT RAISE <class 'pyop2.exceptions.NameTypeError'>