Fix several warnings

[tsalo]

Closes none, but works on #344.

Changes proposed in this pull request

• Replace pkg_resources with aslprep.data.load.
• Add rcond to numpy.linalg.lstsq calls.
• Properly use hue in seaborn calls.
• Set keep_masked_labels to True in NiftiLabelsMasker calls.
  • This change will raise an error in Nilearn 0.15, but that will make it easier to detect and fix.

[effigies]

Thanks so much @effigies! I had no clue data.load could do so much.

https://www.nipreps.org/niworkflows/master/api/niworkflows.data.html

If you add aslprep.data to your API docs, you'll get something similar, listing the available imports for you as well.

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (67607e1) 78.81% compared to head (f1431c0) 79.09%. Report is 2 commits behind head on main.

Files	Patch %	Lines
aslprep/utils/atlas.py	0.00%	4 Missing :warning:
aslprep/cli/workflow.py	66.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #364 +/- ## ========================================== + Coverage 78.81% 79.09% +0.28% ========================================== Files 39 39 Lines 4149 4148 -1 Branches 600 600 ========================================== + Hits 3270 3281 +11 + Misses 685 673 -12 Partials 194 194 ```

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