update external link to GeoJSON spec

[jgravois]

Pull Request check-list

Please make sure to review and check all of these items:

• Does npm run test or npm run test-DIALECT pass with this change (including linting)?
• Does the description below contain a link to an existing issue (Closes #[issue]) or a description of the issue you are solving?
• Have you added new tests to prevent regressions?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Did you update the typescript typings accordingly (if applicable)?
• Did you follow the commit message conventions explained in CONTRIBUTING.md?

Description of change

hi there! 👋
just an update for a stale link in the documentation.

old link: http://geojson.org/geojson-spec.html

new link: https://tools.ietf.org/html/rfc7946

[codecov]

Codecov Report

Merging #12937 (a8526bd) into master (6554992) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #12937   +/-   ##
=======================================
  Coverage   96.32%   96.32%           
=======================================
  Files          95       95           
  Lines        9261     9261           
  Branches       90       90           
=======================================
  Hits         8921     8921           
  Misses        323      323           
  Partials       17       17           

Impacted Files	Coverage Δ
src/data-types.js	91.31% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6554992...a8526bd. Read the comment docs.

[papb]

Hello! I see you are a first-time contributor, thank you for taking the time to help Sequelize! I hope to see more PRs from you in the future!

Recently, we decided to undo some large work that was done on the master branch. For this reason, we needed to "rework" your pull request targeting the new main branch. This was done by @shivamklr in #13067. For this reason, this PR will be closed when that one is merged. I will make sure you get credited for this work in that new commit, as you totally deserve.