Update README.md

[Aurelsicoko]

What does it do?

Update link that warns users before starting using MongoDB.

[codecov]

Codecov Report

Merging #10506 (07fe251) into master (c7c549a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #10506   +/-   ##
=======================================
  Coverage   58.01%   58.01%           
=======================================
  Files         185      185           
  Lines        6431     6431           
  Branches     1400     1400           
=======================================
  Hits         3731     3731           
  Misses       2236     2236           
  Partials      464      464           

Flag	Coverage Δ
front	∅ <ø> (∅)
unit	58.01% <ø> (ø)

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