Fix PR template from fix_lint to fix

Author: ericzolf

.github/PULL_REQUEST_TEMPLATE.md

@@ -3,7 +3,7 @@
 Please, make sure you address all the checklists (for details on how see
 [development documentation](http://tox.readthedocs.org/en/latest/development.html#development))!
 
-- [ ] ran the linter to address style issues (`tox -e fix_lint`)
+- [ ] ran the linter to address style issues (`tox -e fix`)
 - [ ] wrote descriptive pull request text
 - [ ] ensured there are test(s) validating the fix
 - [ ] added news fragment in `docs/changelog` folder