DOC: Autoreformat docstrings.

[Carreau]

This uses an autoreformatter to reformat and fix some of the common
mistakes in numpydoc.

Some of this is purely visual, but other like space before colon in
parameters actually have semantic values. In the case of space before
colon this is to make sure that nupmydoc properly distinguish the
parameter name from its type.

[codecov-commenter]

Codecov Report

Merging #493 (0fa4721) into master (15d3782) will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #493      +/-   ##
==========================================
- Coverage   77.75%   77.70%   -0.06%     
==========================================
  Files         106      106              
  Lines        9269     9256      -13     
  Branches      997      996       -1     
==========================================
- Hits         7207     7192      -15     
- Misses       1706     1707       +1     
- Partials      356      357       +1     

Impacted Files	Coverage Δ
jupyter_server/_sysinfo.py	81.25% <ø> (ø)
jupyter_server/_tz.py	94.44% <ø> (ø)
jupyter_server/auth/login.py	69.76% <ø> (ø)
jupyter_server/base/zmqhandlers.py	59.31% <ø> (ø)
jupyter_server/extension/serverextension.py	75.88% <ø> (ø)
jupyter_server/gateway/managers.py	76.87% <ø> (ø)
jupyter_server/serverapp.py	67.23% <ø> (+0.10%)	⬆️
jupyter_server/services/contents/checkpoints.py	46.51% <ø> (ø)
jupyter_server/services/contents/fileio.py	75.26% <ø> (-0.13%)	⬇️
jupyter_server/services/contents/manager.py	87.76% <ø> (-0.04%)	⬇️
... and 15 more

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[blink1073]

Thank you!