Update Python.gitignore

rectify a mistake that renames a valid record `,cover` and remove a duplicate line for the same purpose. thx @greyltc
ref. https://github.com/github/gitignore/pull/2379

Python.gitignore

@@ -45,8 +45,7 @@ htmlcov/
 .cache
 nosetests.xml
 coverage.xml
-*.cover
-*.py,cover
+*,cover
 .hypothesis/
 .pytest_cache/
 cover/