✏ Fix broken link to newsletter sign-up in docs/help.md

[mborus]

Trying to subscribe to the newletter by clicking on https://sqlmodel.tiangolo.com/newsletter/ gives a 404 error,

Maybe change URL to https://fastapi.tiangolo.com/newsletter/ to make it work?

[codecov]

Codecov Report

Merging #84 (937d3b2) into main (9664c88) will not change coverage.
The diff coverage is n/a.

❗ Current head 937d3b2 differs from pull request most recent head 9ef4154. Consider uploading reports for the commit 9ef4154 to get more accurate results

@@           Coverage Diff           @@
##             main      #84   +/-   ##
=======================================
  Coverage   97.58%   97.58%           
=======================================
  Files         182      182           
  Lines        6054     6054           
=======================================
  Hits         5908     5908           
  Misses        146      146           

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[tiangolo]

Good catch, thank you! 🤓