Remove old hacks to support weird execution environments

Because I want to support new weird execution evironments (to wit
tox-uv).

tox.ini

@@ -6,26 +6,11 @@ passenv =
     PIP_FIND_LINKS
 commands =
     zope-testrunner --test-path=src --tests-pattern='^f?tests$' {posargs:-pvc}
-# Install 'persistent' before installing zodbbrowser because *sigh*
-# pip install collects the packages to be installed before installing them,
-# and some of the packages (BTrees) have a setup_requires=['persistent'], which
-# means setuptools will try to download the persistent egg (despite pip already
-# having downloaded it), and on Rackspace VMs setuptools downloads over HTTPS
-# suffer from mysterious truncation issues that cause md5 hash validation
-# problems that break the build.  My hope is that if 'persistent' is already
-# installed (not just downloaded) then setup.py egg_info will find it and use
-# it instead of attempting to download it again.
-# Upgrade pip because otherwise we can't find lxml wheels because the ABI tag
-# format changed or something.
 extras = test
 deps =
     zope.testrunner
-    persistent
-    pip
-install_command = python -m pip install -U {opts} {packages}
 
 [testenv:py]
-install_command = python -m pip install -U {opts} {packages}
 commands =
     python --version
     zope-testrunner --test-path=src --tests-pattern='^f?tests$' {posargs}