Use tox -e zuul for layout test

Adjust tox environment, the check_projects_yaml_alphabetized.sh script
only works with gerrit/projects.yaml but not with layout.yaml, so remove
the call.

Change the job to use tox -e zuul.

Change-Id: I70d918ec1de94c6ec9aa0c2c6647aa8c791df303

jenkins/jobs/infra.yaml

@@ -34,8 +34,8 @@
     builders:
       - revoke-sudo
       - gerrit-git-prep
-      - shell: |
-          ./tools/run-layout.sh
+      - tox:
+          envlist: 'zuul'
       - zuul_swift_upload_console_log
 
     publishers:

tox.ini

@@ -44,7 +44,6 @@ commands =
 basepython = python2.7
 deps =
 commands =
-  {toxinidir}/tools/check_projects_yaml_alphabetized.sh jenkins/jobs/projects.yaml
   {toxinidir}/tools/run-layout.sh
 
 [testenv:bashate]