CI failing due to bytes as keys

[jacobtomlinson]

Looks like the changes in dask/dask#11757 are causing all of CI here to fail (e.g #9015).

FAILED distributed/http/scheduler/tests/test_scheduler_http.py::test_task_page[123] - TypeError: Unexpected key type <class 'bytes'> (key=b'123')
FAILED distributed/http/scheduler/tests/test_scheduler_http.py::test_task_page[key14] - TypeError: Composite key contains unexpected key type at index=0 (key=(b'123', 1))
FAILED distributed/http/scheduler/tests/test_scheduler_http.py::test_call_stack_page[123] - TypeError: Unexpected key type <class 'bytes'> (key=b'123')
FAILED distributed/http/scheduler/tests/test_scheduler_http.py::test_call_stack_page[key14] - TypeError: Composite key contains unexpected key type at index=0 (key=(b'123', 1))
FAILED distributed/tests/test_client.py::test_bytes_keys - TypeError: Unexpected key type <class 'bytes'> (key=b'inc-123')