Cleanup tox environment

Since we do not build DocBook XML anymore, we have removed the jobs for
this and thus can remove the support for these also from tox.ini.

checksyntax, checklinks and checkdeletions are DocBook XML only targets,
so remove them.

Change-Id: Iaa663c03fd6e2976208e20ba03dbab4d8d82b2ce
Depends-On: I9f5944eb9db06fe2ff9088f22048c198b2921237

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 1.6
-envlist = checkniceness,checksyntax,checkdeletions,checkbuild,checklinks
+envlist = checkniceness,checkbuild
 skipsdist = True
 
 [testenv]
@@ -18,9 +18,6 @@ whitelist_externals =
 [testenv:venv]
 commands = {posargs}
 
-[testenv:checklinks]
-commands = openstack-doc-test --check-links {posargs}
-
 [testenv:linkcheck]
 commands =
   {toxinidir}/tools/build-all-rst.sh --linkcheck
@@ -30,15 +27,7 @@ commands =
   openstack-doc-test --check-niceness {posargs}
   flake8
   doc8 doc
-
-[testenv:checksyntax]
-commands =
-    openstack-doc-test --check-syntax {posargs}
-    # Check that .po and .pot files are valid:
-    bash -c "find doc -type f -regex '.*\.pot?' -print0|xargs -0 -n 1 msgfmt --check-format -o /dev/null"
-
-[testenv:checkdeletions]
-commands = openstack-doc-test --check-deletions {posargs}
+  bash -c "find doc -type f -regex '.*\.pot?' -print0|xargs -0 -n 1 msgfmt --check-format -o /dev/null"
 
 [testenv:checkbuild]
 commands =