Reformat from new black version

[AdamGleave]

black upgrade made some changes to formatting: reformat to be consistent with linter.

[codecov]

Codecov Report

Merging #38 into master will decrease coverage by 3.09%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##            master      #38      +/-   ##
===========================================
- Coverage   100.00%   96.90%   -3.10%     
===========================================
  Files           24       24              
  Lines          646      646              
===========================================
- Hits           646      626      -20     
- Misses           0       20      +20     

Impacted Files	Coverage Δ
src/seals/base_envs.py	100.00% <ø> (ø)
src/seals/diagnostics/branching.py	100.00% <ø> (ø)
src/seals/diagnostics/early_term.py	100.00% <ø> (ø)
src/seals/diagnostics/init_shift.py	100.00% <ø> (ø)
src/seals/diagnostics/largest_sum.py	100.00% <ø> (ø)
src/seals/diagnostics/noisy_obs.py	100.00% <ø> (ø)
src/seals/diagnostics/risky_path.py	100.00% <ø> (ø)
src/seals/diagnostics/sort.py	100.00% <ø> (ø)
src/seals/mujoco.py	100.00% <ø> (ø)
src/seals/testing/envs.py	100.00% <ø> (ø)
... and 6 more

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