Drop environments for nose

Horizon dropped its usage of nose in 14.0.0[1] and these environments
have been unused since then.

[1] 1f80d94459856a8c477310cc0fe4b0e165d8c0c1

Also drop the VIRTUAL_ENV environment which is now automatically set
by tox.

Change-Id: I7c28282d9fb1a2e8c59d4757fec4e8ef60d0401e

tox.ini

@@ -6,13 +6,7 @@ ignore_basepython_conflict=true
 [testenv]
 usedevelop = True
 basepython = python3
-setenv = VIRTUAL_ENV={envdir}
+setenv = DJANGO_SETTINGS_MODULE=ironic_ui.test.settings
-         NOSE_WITH_OPENSTACK=1
-         NOSE_OPENSTACK_COLOR=1
-         NOSE_OPENSTACK_RED=0.05
-         NOSE_OPENSTACK_YELLOW=0.025
-         NOSE_OPENSTACK_SHOW_ELAPSED=1
-         DJANGO_SETTINGS_MODULE=ironic_ui.test.settings
 deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
        -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
@@ -109,4 +103,4 @@ deps = codespell
 # note(JayF): {posargs} lets us run `tox -ecodespell -- -w` to get codespell
 #             to correct spelling issues in our code it's aware of.
 commands =
-  codespell {posargs}
+  codespell {posargs}