Fix broken links (getzola.com -> getzola.org)

[reujab]

IMPORTANT: Please do not create a Pull Request adding a new feature without discussing it first.

The place to discuss new features is the forum: https://zola.discourse.group/
If you want to add a new feature, please open a thread there first in the feature requests section.

Sanity check:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Code changes

(Delete or ignore this section for documentation changes)

• Are you doing the PR on the next branch?

No. CONTRIBUTING.md:

As the documentation site is automatically built on commits to master, all development happens on the next branch, unless it is fixing the current documentation.

If the change is a new feature or adding to/changing an existing one:

• Have you created/updated the relevant documentation page(s)?

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I noticed a few references to getzola.com, when the correct url is getzola.org.

[c-git]

Interesting catch, I wonder why it wasn't picked up by zola check.

[Keats]

I'm not very good at running zola check

[Keats]

Thanks!