UPDATE: Drop Python 3.7, add Python 3.11, unpin myst-nb in docs

[choldgraf]

A few version updates:

• Drop python 3.7 and add 3.11 (3.7 is losing security support in a two months)
• Unpin myst-nb which was making packaging hard

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@73817a4). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #96   +/-   ##
=======================================
  Coverage        ?   83.30%           
=======================================
  Files           ?       20           
  Lines           ?     1354           
  Branches        ?        0           
=======================================
  Hits            ?     1128           
  Misses          ?      226           
  Partials        ?        0           

Flag	Coverage Δ
pytests	83.30% <0.00%> (?)

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