Fix code coverage in Travis

The src path is already specified in .coveragerc

Author: Cito

.travis.yml

@@ -22,7 +22,7 @@ install:
   - pip install "poetry>=1.0.0a5"
   - poetry install
 script:
-  - tox -e $TOXENV -- --cov-report term-missing --cov=src
+  - tox -e $TOXENV -- --cov-report term-missing --cov=graphql_relay
 after_success:
   - codecov
 deploy: