Added "hdk" to the _force_execution_mode description #282

Job	Run time
lint (black)	24s
lint (mypy)	3m 14s
lint (flake8)	24s
test api	4m 33s
test-headers	4m 11s
test-no-engine	3m 39s
lint (pydocstyle)	0s
test-clean-install-ubuntu	1m 25s
test-ubuntu (engine unidist mpi, python 3.8)	52m 29s
test-clean-install-windows	3m 55s
test cloud	4m 56s
test-ubuntu (engine python, python 3.8, group_1)	33m 15s
test-ubuntu (engine ray, python 3.8, group_1)	30m 56s
test-ubuntu (engine ray, python 3.8, group_2)	11m 12s
test-ubuntu (engine ray, python 3.8, group_3)	17m 6s
test-ubuntu (engine ray, python 3.8, group_4)	52m 35s
test-ubuntu (engine dask, python 3.8, group_1)	36m 50s
test-ubuntu (engine dask, python 3.8, group_2)	28m 44s
test-ubuntu (engine dask, python 3.8, group_3)	44m 49s
test-ubuntu (engine dask, python 3.8, group_4)	54m 39s
Test BaseOnPython execution, Python 3.8	25m 30s
test experimental	11m 29s
Test HDK storage format, Python 3.8	23m 35s
test-internals	9m 58s
test-asv-benchmarks	0s
test (pyarrow, python 3.8)	6m 10s
test-spreadsheet (engine ray, python 3.8)	4m 6s
test-spreadsheet (engine dask, python 3.8)	4m 13s
test-windows (engine ray, python 3.8, group_1)	43m 31s
test-windows (engine ray, python 3.8, group_2)	30m 28s
test-windows (engine ray, python 3.8, group_3)	1h 29m 6s
test-windows (engine ray, python 3.8, group_4)	2h 10m 0s
test-windows (engine dask, python 3.8, group_1)	35m 44s
test-windows (engine dask, python 3.8, group_2)	37m 33s
test-windows (engine dask, python 3.8, group_3)	1h 11m 31s
test-windows (engine dask, python 3.8, group_4)	1h 32m 8s
upload-coverage	17s
	16h 44m 35s

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