[pylint] Remove lint tox environment

We don't use the tools/lintstack.py
script anymore since its removal in [1],
so cleanup the unused tox environment and
the gitignore corresponding files.

TrivialFix

[1] https://review.openstack.org/#/c/609791/
Change-Id: Id2d40c1f9f1ce71a22ba9836b90c3e917171a556

.gitignore

@@ -29,8 +29,6 @@ keys
 local_settings.py
 subunit.log
 tools/conf/manila.conf*
-tools/lintstack.head.py
-tools/pylint_exceptions
 tags
 # Files created by Sphinx build
 doc/build

tox.ini

@@ -109,12 +109,6 @@ deps = -r{toxinidir}/requirements.txt
 whitelist_externals = bash
 commands = bash ./tools/coding-checks.sh --pylint {posargs}
 
-[testenv:lint]
-basepython = python3
-deps = -r{toxinidir}/requirements.txt
-       pylint==1.9.0
-commands = python tools/lintstack.py check
-
 [testenv:api-ref]
 basepython = python3
 # This environment is called from CI scripts to test and publish