tox: Reduce dependencies for cxfreeze-windows.

tox.ini

@@ -201,7 +201,9 @@ commands =
 # fail if we didn't have a fallback defined.
 basepython = {env:PYTHON:}/python.exe
 skip_install = true
-deps = {[testenv:smoke-frozen]deps}
+deps =
+    -r{toxinidir}/requirements.txt
+    cx_Freeze==4.3.4
 commands =
     {envpython} scripts/link_pyqt.py --tox {envdir}
     {envpython} scripts/dev/freeze.py {posargs}