fix: switch some python:3 images to use the -slim variant #2003

Job	Run time
ci (kubernetes, ./tests/bin/ci.sh -e 'test(7.\|8.)\|python.*', ubuntu-latest)	1m 40s
ci (kubernetes, ./tests/bin/ci.sh -i 'test7.' -e 'test7(b.\|c.\|d.\|e.\|f.\|g.\|h.)', ubuntu-la...	3m 24s
ci (kubernetes, ./tests/bin/ci.sh -i 'test7(b.\|c.\|d.\|e.\|g.\|h.)', ubuntu-latest)	3m 24s
ci (kubernetes, ./tests/bin/ci.sh -i 'test7f.*', ubuntu-latest)	5m 4s
ci (kubernetes, ./tests/bin/ci.sh -i 'test8.*', ubuntu-latest)	2m 37s
ci (kubernetes, /tmp/lunchpail bat demos/data-prep-kit --concurrency 1 --auto-clean --target=$LUN...	3m 18s
ci (kubernetes, ./tests/bin/go.sh, ubuntu-latest)	1m 31s
ci (kubernetes, ./tests/bin/pipelines.sh, ubuntu-latest)	3m 23s
ci (local, ./tests/bin/ci.sh -e 'test(7.\|8.)\|python.*', ubuntu-latest)	28s
ci (local, ./tests/bin/ci.sh -i 'test7.' -e 'test7(b.\|c.\|d.\|e.\|f.\|g.\|h.)', ubuntu-latest)	2m 56s
ci (local, ./tests/bin/ci.sh -i 'test7(b.\|c.\|d.\|e.\|g.\|h.)', ubuntu-latest)	2m 17s
ci (local, ./tests/bin/ci.sh -i 'test7f.*', ubuntu-latest)	2m 12s
ci (local, ./tests/bin/ci.sh -i 'test8.*', ubuntu-latest)	19s
ci (local, /tmp/lunchpail bat demos/data-prep-kit --concurrency 1 --auto-clean --target=$LUNCHPAI...	3m 24s
ci (local, ./tests/bin/go.sh, ubuntu-latest)	1m 40s
ci (local, ./tests/bin/pipelines.sh, ubuntu-latest)	2m 16s
	39m 53s

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