fix: switch some python:3 images to use the -slim variant #2007

Job	Run time
ci (kubernetes, ./tests/bin/ci.sh -e 'test(7.\|8.)\|python.*', ubuntu-latest)	2m 0s
ci (kubernetes, ./tests/bin/ci.sh -i 'test7.' -e 'test7(b.\|c.\|d.\|e.\|f.\|g.\|h.)', ubuntu-la...	2m 35s
ci (kubernetes, ./tests/bin/ci.sh -i 'test7(b.\|c.\|d.\|e.\|g.\|h.)', ubuntu-latest)	2m 36s
ci (kubernetes, ./tests/bin/ci.sh -i 'test7f.*', ubuntu-latest)	2m 36s
ci (kubernetes, ./tests/bin/ci.sh -i 'test8.*', ubuntu-latest)	2m 17s
ci (kubernetes, /tmp/lunchpail bat demos/data-prep-kit --concurrency 1 --auto-clean --target=$LUN...	2m 36s
ci (kubernetes, ./tests/bin/go.sh, ubuntu-latest)	1m 27s
ci (kubernetes, ./tests/bin/pipelines.sh, ubuntu-latest)	4m 36s
ci (local, ./tests/bin/ci.sh -e 'test(7.\|8.)\|python.*', ubuntu-latest)	25s
ci (local, ./tests/bin/ci.sh -i 'test7.' -e 'test7(b.\|c.\|d.\|e.\|f.\|g.\|h.)', ubuntu-latest)	2m 36s
ci (local, ./tests/bin/ci.sh -i 'test7(b.\|c.\|d.\|e.\|g.\|h.)', ubuntu-latest)	2m 15s
ci (local, ./tests/bin/ci.sh -i 'test7f.*', ubuntu-latest)	2m 13s
ci (local, ./tests/bin/ci.sh -i 'test8.*', ubuntu-latest)	30s
ci (local, /tmp/lunchpail bat demos/data-prep-kit --concurrency 1 --auto-clean --target=$LUNCHPAI...	1m 51s
ci (local, ./tests/bin/go.sh, ubuntu-latest)	1m 33s
ci (local, ./tests/bin/pipelines.sh, ubuntu-latest)	1m 59s
	34m 5s

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