Fix travis warning

```
jobs.include.deploy: deprecated key skip_cleanup (not supported in dpl v2, use cleanup)
```

Signed-off-by: Ivan Kanakarakis <ivan.kanak@gmail.com>

Author: c00kiemon5ter

.travis.yml

@@ -68,7 +68,7 @@ jobs:
         - provider: pypi
           distributions: sdist bdist_wheel
           server: "https://test.pypi.org/legacy/"
-          skip_cleanup: true
+          cleanup: false
           username: "__token__"
           password: "$PYPI_PRE_RELEASE_TOKEN"
           on: