Python: Configure Black for Python 3.8-3.12

Our previous Black `target-version`, `py36`, reached its end-of-life
date some time ago. In fact, `py37` is already unsupported, as well.

In addition, according to the Black docs, we should configure for
_all_ supported versions, not simply a minimum.[1]

So, set the targeted Pythons to `py38` through `py312` inclusive.

[1]: https://black.readthedocs.io/en/stable/usage_and_configuration/the_basics.html#command-line-options

pyproject.toml

@@ -4,5 +4,5 @@
 
 [tool.black]
 line-length = 80
-target-version = ['py36']
+target-version = ['py38', 'py39', 'py310', 'py311', 'py312']
 include = 'nautilus-extension/.*\.py$'