edit GitLab license info in regards to CC licensing

What does this MR do?

This commit updates the LICENSE file so that it contains only the exact text of the MIT license. It moves the reference to Creative Commons licensing (for the docs) to the README.

Are there points in the code the reviewer needs to double check?

No.

Why was this MR needed?

GitHub uses a library called Licensee to identify a project's license type. It shows this information in the status bar and via the API if it can unambiguously identify the license.

My previous MR (edit GitLab license info so that GitHub recognizes it) updated the LICENSE and README files so that Licensee was able to detect GitLab-CE's MIT license.

A recent MR added a note to the LICENSE file in regards to the CC licensing for GitLab documentation. Because the LICENSE file no longer contains only the text of the MIT license, Licensee isn't currently able to detect the repo's license type.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

N/A