Update webhook doc link

[derrickmehaffy]

What does it do?

Replaced link in webhooks page with proper documentation link

Why is it needed?

Doc link for webhooks returned a 404

How to test it?

Run Strapi application, go to settings => webhook and click on the documentation link

Related issue(s)/PR(s)

fixes #10294

[codecov]

Codecov Report

Merging #10309 (0f62c01) into master (f46d1e2) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #10309   +/-   ##
=======================================
  Coverage   57.84%   57.84%           
=======================================
  Files         184      184           
  Lines        6395     6395           
  Branches     1396     1396           
=======================================
  Hits         3699     3699           
  Misses       2233     2233           
  Partials      463      463           

Flag	Coverage Δ
front	∅ <ø> (∅)
unit	57.84% <ø> (ø)

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[pwizla]

LGTM, thank you Derrick!