Enable back setuptools automatic discovery

Automatic package discovery by setuptools was disabled in commit
8a5fa22, somehow as a workaround for an issue RPM build system
(rpm-software-management/rpm#2532) or maybe
because it was misconfigured then.

However, having to declare packages explicitly (options 'packages' in
'[tool.setuptools]' section of pyproject.toml) is tedious and
error-prone as shown in #411
which indicates that we were missing some sub-packages.

In the meantime, the RPM issue got resolved, so it seems safe to get
back to automatic discovery as this resolves the later issue in a more
future-proof way than explicitly listing packages.

So we get back to automatic discovery here, although not using
[tool.setuptools.packages.find], but simply letting setuptools discover
the "flat-layout" we're using, as can be seen by the following messages
from 'python -m build' un:

    * Building sdist...
    No `packages` or `py_modules` configuration, performing automatic discovery.
    `flat-layout` detected -- analysing .
    discovered packages -- ['pgactivity', 'pgactivity.profiles', 'pgactivity.queries']

This requires no configuration as we use common excluded names (like
'tests', 'docs').

CHANGELOG.md

@@ -10,6 +10,7 @@
 ### Misc
 
 * Turn Python warnings into errors when running the test suite.
+* Enable (back) setuptools "automatic discovery" (#411).
 
 ## pg\_activity 3.5.0 - 2024-03-01
 

pyproject.toml

@@ -84,9 +84,6 @@ Homepage = "https://github.com/dalibo/pg_activity"
 [tool.setuptools.dynamic]
 version = { attr = "pgactivity.__version__" }
 
-[tool.setuptools]
-packages = ["pgactivity"]
-
 [tool.black]
 line-length = 88
 include = '\.pyi?$'