fix: use module name for pytest-cov coverage collection

The --cov flag was using {{package}} (jsonlt-python) instead of
{{module}} (jsonlt), causing pytest-cov to fail to find the module
and generate empty coverage reports.

Author: tbhb

Justfile

@@ -160,7 +160,7 @@ test-conformance *args:
 
 # Run tests with coverage
 test-coverage *args:
-  pytest -m "not benchmark" --cov={{package}} --cov-branch --cov-report=term-missing:skip-covered --cov-report=xml --cov-report=json "$@"
+  pytest -m "not benchmark" --cov={{module}} --cov-branch --cov-report=term-missing:skip-covered --cov-report=xml --cov-report=json "$@"
 
 # RUn documentation tests
 test-examples *args: