minor #20253 [Testing] Remove an old article (javiereguiluz)

This PR was merged into the 7.1 branch.

Discussion
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[Testing] Remove an old article

We soft-deleted this article in 5.x version, so let's delete it for real in 7.x branches.

Commits
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e157327 [Testing] Remove an old article

Author: javiereguiluz

_build/redirection_map

@@ -568,3 +568,4 @@
 /messenger/multiple_buses /messenger#messenger-multiple-buses
 /frontend/encore/server-data /frontend/server-data
 /components/string /string
+/testing/http_authentication /testing#testing_logging_in_users