perf(travis): improve `salt-lint` invocation [skip ci]

* Automated using https://github.com/myii/ssf-formula/pull/90

.travis.yml

         # Install and run `salt-lint`
         - pip install --user salt-lint
         - git ls-files | grep '\.sls$\|\.jinja$\|\.j2$\|\.tmpl$\|\.tst$'
-                       | xargs -I {} salt-lint {}
+                       | xargs salt-lint
         # Install and run `yamllint`
         # Need at least `v1.17.0` for the `yaml-files` setting
         - pip install --user yamllint>=1.17.0
     - env: INSTANCE=v201707-py2-centos-6-2017-7-py2
     # - env: INSTANCE=v201707-py2-amazonlinux-2-2017-7-py2
     # - env: INSTANCE=v201707-py2-arch-base-latest-2017-7-py2
-    # - env: INSTANCE=v201803-py2-debian-9-2018-3-py2
+    - env: INSTANCE=v201803-py2-debian-9-2018-3-py2
     # - env: INSTANCE=v201803-py2-ubuntu-1604-2018-3-py2
     - env: INSTANCE=v201803-py2-centos-7-2018-3-py2
-    - env: INSTANCE=v201803-py2-amazonlinux-2-2018-3-py2
+    # - env: INSTANCE=v201803-py2-amazonlinux-2-2018-3-py2
     # - env: INSTANCE=v201803-py2-arch-base-latest-2018-3-py2
-    - env: INSTANCE=v201902-py2-debian-9-2019-2-py2
     - env: INSTANCE=v201902-py2-ubuntu-1804-2019-2-py2
     # - env: INSTANCE=v201902-py2-centos-7-2019-2-py2
-    # - env: INSTANCE=v201902-py2-opensuse-leap-151-2019-2-py2
-    # - env: INSTANCE=v201902-py2-amazonlinux-2-2019-2-py2
+    - env: INSTANCE=v201902-py2-amazonlinux-2-2019-2-py2
     # - env: INSTANCE=v201902-py2-arch-base-latest-2019-2-py2
-    # - env: INSTANCE=v201902-py3-debian-10-2019-2-py3
+    - env: INSTANCE=v201902-py3-debian-10-2019-2-py3
+    # - env: INSTANCE=v201902-py3-debian-9-2019-2-py3
     # - env: INSTANCE=v201902-py3-ubuntu-1804-2019-2-py3
     # - env: INSTANCE=v201902-py3-centos-8-2019-2-py3
-    - env: INSTANCE=v201902-py3-fedora-31-2019-2-py3
     - env: INSTANCE=v201902-py3-opensuse-leap-151-2019-2-py3
 
     ## Define the release stage that runs `semantic-release`