Remove codecov

For some reason, the codecov package on PyPI is gone.
They seem to have been deprecating their old upload method,
and we don't care enough about code coverage for it to block
this release.

.gitlab-ci.yml

@@ -20,7 +20,7 @@ include:
   before_script:
     # Custom line to install our own deps from Git using GitLab CI credentials
     - "pip install -e git+https://gitlab-ci-token:${CI_JOB_TOKEN}@gitlab.com/teklia/arkindex/transkribus#egg=transkribus-client"
-    - pip install -r tests-requirements.txt codecov
+    - pip install -r tests-requirements.txt
     - "echo 'database: {host: postgres, port: 5432}\npublic_hostname: http://ci.arkindex.localhost' > $CONFIG_PATH"
 
   # Those jobs require the base image; they might fail if the image is not up to date.
@@ -61,7 +61,6 @@ backend-tests:
 
   script:
     - python3 setup.py test
-    - codecov
 
 backend-lint:
   image: python:3.10