MINOR: stream: Add level 7 retries on http error 401, 403

Level-7 retries are only possible with a restricted number of HTTP
return codes. While it is usually not safe to retry on 401 and 403, I
came up with an authentication backend which was not synchronizing
authentication of users. While not perfect, being allowed to also retry
on those return codes is really helpful and acts as a hotfix until we
can fix the backend.

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>
diff --git a/doc/configuration.txt b/doc/configuration.txt
index d25b729..ab49c68 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -9320,10 +9320,11 @@
                         rejected by the server. These requests are generally
                         considered to be safe to retry.
 
-      <status>          any HTTP status code among "404" (Not Found), "408"
-                        (Request Timeout), "425" (Too Early), "500" (Server
-                        Error), "501" (Not Implemented), "502" (Bad Gateway),
-                        "503" (Service Unavailable), "504" (Gateway Timeout).
+      <status>          any HTTP status code among "401" (Unauthorized), "403"
+                        (Forbidden), "404" (Not Found), "408" (Request Timeout),
+                        "425" (Too Early), "500" (Server Error), "501" (Not
+                        Implemented), "502" (Bad Gateway), "503" (Service
+                        Unavailable), "504" (Gateway Timeout).
 
       all-retryable-errors
                         retry request for any error that are considered