pyproject.toml: simplify coverage filter

Drop the "omit" rules and use a simpler "source = src/" to declare
what we are interested in. This is the first recommendation at
https://coverage.readthedocs.io/en/latest/source.html#source-execution

Note: as seen in the logs, Github runners don't use /tmp. They may not
even use $TMPDIR.

Signed-off-by: Marc Herbert <Marc.Herbert@gmail.com>

Author: marc-hb

pyproject.toml

@@ -69,16 +69,7 @@ namespaces = false
 [tool.coverage.run]
 patch = ["subprocess"]
 relative_files = true
-omit = [
-  "*/tmp/*",
-]
-
-[tool.coverage.report]
-omit = [
-  "*/tmp/*",
-  "*/net-tools/scripts/*",
-  "*/subdir/Kconfiglib/scripts/test.py",
-]
+source = ["src/"]
 
 [tool.coverage.paths]
 source = [