Set default verbosity of pytest to 1

This is equivalent to the `-v` option, which e.g. shows each test inside a
file as a separate line in the output, showing the reason why a test was
skipped.

xref. https://docs.pytest.org/en/7.1.x/how-to/output.html#verbosity

pytest.ini

@@ -1,3 +1,4 @@
 [pytest]
+addopts = --verbosity=1
 markers =
     tests_galaxy_branch: test against a specific Galaxy branch