Updating the docs to discourage HTTP usage when there's no downside to HTTPS usage.

Took it from https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/3232

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Split into user and administrator docs:

- administration/issue_closing_pattern.md
- user/project/issues/automatic_issue_closing.md

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The only major difference with the EE version is the change from a light and dark logo to only a header logo
The dark logo wasn't used anyway, so it seemed to make sense to me to rename the field to the actual function of it

Added phrase "Here's how to close multiple issues in one commit message" so that doc is easier to find by users

capitalized.

Make the plural version consistently "URLs".

Fix an instance where the article "the" before URL was missing.