Use importlib-metadata<5.0.0 on older python/salt

Uses importlib-metadata<5.0.0 for python3.7 on 3004.2 and 3005.1 to
work around a bug in salt.utils.entrypoints when using
pytest-salt-factories.

tox.ini

@@ -9,6 +9,7 @@ deps = -r{toxinidir}/tests/requirements.txt
     v3004.2: salt<3004.2
     v3004.2: jinja2<3.1
     v3005.1: salt<3005.1
+    py3.7-{cherrypy,tornado}-{v3004.2,v3005.1}: importlib-metadata<5.0.0
     master: git+https://github.com/saltstack/salt.git@master#egg=salt
 
 changedir = {toxinidir}