minor #14984 [Messenger] Remove duplicated Redis transport requirements (sebpacz)

This PR was merged into the 5.2 branch.

Discussion
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[Messenger] Remove duplicated Redis transport requirements

The Redis transport requirements has been presented twice. I mean the following sentences:

> This transport requires the Redis PHP extension (>=4.3) and a running Redis server (^5.0).

> To use the Redis transport, you will need the Redis PHP extension (>=4.3) and a running Redis server (^5.0).
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Commits
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d6a7314 [Messenger] Remove duplicated Redis transport requirements

Author: javiereguiluz

messenger.rst

@@ -1164,9 +1164,6 @@ The Redis transport DSN may looks like this:
 
     The Unix socket DSN was introduced in Symfony 5.1.
 
-To use the Redis transport, you will need the Redis PHP extension (>=4.3) and
-a running Redis server (^5.0).
-
 A number of options can be configured via the DSN or via the ``options`` key
 under the transport in ``messenger.yaml``: