Revert "Add codecov report to travis.yml"

This reverts commit c378d1f18b.

.travis.yml

@@ -2,8 +2,3 @@ language: node_js
 node_js:
   - "8"
   - "10"
-install:
-  - npm install -g codecov
-script:
-  - npm run test
-  - codecov