Revert "Treat XPASS status as a test failure"

For its immediate goal, this facilitated identifying the XPASS
status of TestSubmodule.test_rename and verifying that the revised
xfail condition eliminated it.

In the test output, XPASS is written as a failure, with strict
xfail behavior noted. Contributors less familiar with marking tests
xfail may mistake this to mean some behavior of the code under test
was broken. So if strict_xfail is to be enabled, it might be best
to do that in a pull request devoted to it, and maybe even to add
to the docs, about how to recognize and handle newly xpassing
tests.

This reverts commit 0f8cd4c.

pyproject.toml

@@ -8,7 +8,6 @@ filterwarnings = "ignore::DeprecationWarning"
 python_files = "test_*.py"
 tmp_path_retention_policy = "failed"
 testpaths = "test"  # Space separated list of paths from root e.g test tests doc/testing.
-xfail_strict = true  # Treat the XPASS status as a test failure (unless strict=False is passed).
 # --cov   coverage
 # --cov-report term  # send report to terminal term-missing -> terminal with line numbers  html  xml
 # --cov-report term-missing # to terminal with line numbers