Update contributing.rst

Author: Uma-95

src/user/contributing.rst

@@ -49,7 +49,7 @@ We are glad to know that you would like to contribute to the ``conda-forge`` doc
 5. Submit a `pull request
    <https://help.github.com/articles/about-pull-requests/>`_ to the main repository proposing your changes.
 
-   Writing guidelines:
+Writing guidelines:
 
 Some basic writing guidelines should be kept in mind before you start contributing: