CI/CD coverage docs: fix pytest-cov regex

adapted regular expression to correctly parse total coverage when using pytest-cov

> ----------- coverage: platform linux, python 3.6.6-final-0 -----------
> Name                      Stmts   Miss  Cover
> ---------------------------------------------
> integrade/__init__.py         0      0   100%
> integrade/api.py             86      0   100%
> integrade/config.py          36      1    97%
> integrade/exceptions.py       3      0   100%
> integrade/utils.py           11      0   100%
> tests/test_api.py           153      0   100%
> tests/test_config.py         46      0   100%
> tests/test_integrade.py       6      0   100%
> tests/test_utils.py          12      0   100%
> ---------------------------------------------
> TOTAL                       353      1    99%

issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/48613

app/views/projects/settings/ci_cd/_form.html.haml

@@ -91,7 +91,7 @@
                 %code \(\d+.\d+\%\) covered
               %li
                 pytest-cov (Python) -
-                %code \d+\%\s*$
+                %code ^TOTAL\s+\d+\s+\d+\s+(\d+\%)$
               %li
                 phpunit --coverage-text --colors=never (PHP) -
                 %code ^\s*Lines:\s*\d+.\d+\%