Remove `python -m pip install pillow tifffile` from CI #337

Job	Run time
Setup cache and determine changed repositories (3.11)	4m 15s
Lint tool-list (3.11)	32s
Lint Python scripts (3.11)	18s
Check file sizes	7s
Lint R scripts (ubuntu-20.04, release)	1m 5s
Test tools (0, 3.11)	3m 24s
Combine chunked test results (3.11)	58s
Check workflow success	1s
Deploy	0s
Report deploy status	0s
	10m 40s

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