minor #20200 Update link for accelerated downloads on nginx (nicolas-grekas)

This PR was submitted for the 7.1 branch but it was merged into the 5.4 branch instead.

Discussion
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Update link for accelerated downloads on nginx

The existing link is dead.

Commits
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afe3aea Update link for accelerated downloads on nginx

Author: OskarStark

components/http_foundation.rst

@@ -857,7 +857,7 @@ Learn More
     /session
     /http_cache/*
 
-.. _nginx: https://www.nginx.com/resources/wiki/start/topics/examples/xsendfile/
+.. _nginx: https://mattbrictson.com/blog/accelerated-rails-downloads
 .. _Apache: https://tn123.org/mod_xsendfile/
 .. _`JSON Hijacking`: https://haacked.com/archive/2009/06/25/json-hijacking.aspx/
 .. _`valid JSON top-level value`: https://www.json.org/json-en.html