Remove install unnecessary packages

The docs requirements migrated to doc/requirements.txt
we need not install things from requirements.txt.

Change-Id: I947ab7ced3454cf0ad2e5ef9c3d75467f3e620b6

tox.ini

@@ -10,8 +10,7 @@ basepython = python3
 usedevelop = True
 setenv =
    VIRTUAL_ENV={envdir}
-deps = -r{toxinidir}/requirements.txt
-       -r{toxinidir}/test-requirements.txt
+deps = -r{toxinidir}/test-requirements.txt
 commands = stestr run --slowest {posargs}
 
 [testenv:venv]
@@ -22,7 +21,6 @@ commands = sphinx-build -a -W -b html doc/source doc/build/html
 
 [testenv:spelling]
 deps =
-   -r{toxinidir}/requirements.txt
    sphinxcontrib-spelling
    PyEnchant
 commands = sphinx-build -b spelling doc/source doc/build/spelling