minor #18809 Add information about timeout semantics for redis option timeout (andrew-demb)

This PR was submitted for the 6.1 branch but it was merged into the 6.3 branch instead.

Discussion
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Add information about timeout semantics for redis option `timeout`

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Lowest branch with introduced `timeout` option - `6.1`

Commits
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e3550df Add information about timeout semantics for redis option `timeout`

Author: javiereguiluz

messenger.rst

@@ -1624,8 +1624,8 @@ persistent_id            String, if null connection is          null
 retry_interval           Int, value in milliseconds             ``0``
 read_timeout             Float, value in seconds                ``0``
                          default indicates unlimited
-timeout                  Float, value in seconds                ``0``
-                         default indicates unlimited
+timeout                  Connection timeout. Float, value in    ``0``
+                         seconds default indicates unlimited
 sentinel_master          String, if null or empty Sentinel      null
                          support is disabled
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