Fix broken url of "Imporove this page" button in docs

[saintmalik]

Hello Guys,

On the Configuring Build Notifications page, the Improve this page Button is broken but checking it manually on the github repo, noticed it was renamed, and it seems the dead link can only be fix by the internal team.

Here is the broken link: https://github.com/travis-ci/docs-travis-ci-com/edit/master/user/notifications.md

Here is the correct link: https://github.com/travis-ci/docs-travis-ci-com/edit/master/user/notifications.md.erb

Thanks.

[stale[bot]]

Thanks for contributing to this issue. As it has been 90 days since the last activity, we are automatically closing the issue. This is often because the request was already solved in some way and it just wasn't updated or it's no longer applicable. If that's not the case, please do feel free to either reopen this issue or open a new one. We'll gladly take a look again! You can read more here: https://blog.travis-ci.com/2018-03-09-closing-old-issues