Tox: simplify pypy command

Previously in CI, pypy tests would hang forever due to https://foss.heptapod.net/pypy/pypy/-/issues/3317.
This was fixed in the latest release, so we can remove the workaround.

tox.ini

@@ -37,22 +37,17 @@ skip_install = True
 recreate = True
 deps =
     -r{toxinidir}/test_requirements.txt
-; a separate worker is required in ci due to https://foss.heptapod.net/pypy/pypy/-/issues/3317
-; this seems to cause tox to wait forever
-; remove this when pypy releases the bugfix
 commands =
     pip install -e .[d]
     coverage erase
     pytest tests --run-optional no_python2 \
         --run-optional no_jupyter \
         !ci: --numprocesses auto \
-        ci: --numprocesses 1 \
         --cov {posargs}
     pip install -e .[jupyter]
     pytest tests --run-optional jupyter \
         -m jupyter \
         !ci: --numprocesses auto \
-        ci: --numprocesses 1 \
         --cov --cov-append {posargs}
     coverage report