CI: Change coverage directory name to `htmlcov` (#433)

Default pytest and mkdocs-coverage directory

.gitlab-ci.yml

@@ -116,10 +116,10 @@ tests:3.12:cov:
   coverage: '/(?i)total.*\s+(\d+%)/'
   script:
     - poetry install --extras deathreaper
-    - poetry run pytest --cov silkaj --cov-report html:cov_html --cov-report xml --cov-report term
+    - poetry run pytest --cov silkaj --cov-report html --cov-report xml --cov-report term
   artifacts:
     paths:
-      - cov_html
+      - htmlcov
       - coverage.xml
     expire_in: 2 days
     reports: