Travis CI: replace Python 3.9 dev with 3.9 release

Removed it from the 'allow_failures' block too.

Signed-off-by: JoeLametta <[email protected]>

.travis.yml

@@ -11,7 +11,7 @@ python:
   - "3.6"
   - "3.7"
   - "3.8"
-  - "3.9-dev"
+  - "3.9"
 virtualenv:
   system_site_packages: false
 
@@ -23,7 +23,6 @@ env:
 jobs:
   allow_failures:
    - python: "3.5"
-   - python: "3.9-dev"
   include:
   - python: 3.8
     env: FLAKE8=true