[data.hivtb] Minor adjustments

src/ptbench/data/hivtb/datamodule.py

src/ptbench/data/hivtb/fold_0.py

src/ptbench/data/hivtb/fold_1.py

src/ptbench/data/hivtb/fold_2.py

src/ptbench/data/hivtb/fold_3.py

src/ptbench/data/hivtb/fold_4.py

src/ptbench/data/hivtb/fold_5.py

src/ptbench/data/hivtb/fold_6.py

src/ptbench/data/hivtb/fold_7.py

src/ptbench/data/hivtb/fold_8.py

src/ptbench/data/hivtb/fold_9.py