sentry: Reduce http timeout.

This helps reduce the impact on busy uwsgi processes in case there are
slow timeout failures of Sentry servers.  The p99 is less than 300ms,
and p99.9 per day peaks at around 1s, so this will not affect more
than .1% of requests in normal operation.

This is not a complete solution (see #26229); it is merely stop-gap
mitigation.

(cherry picked from commit a076d49be7)

zerver/views/sentry.py

@@ -14,7 +14,7 @@ from zerver.lib.validator import check_url, to_wild_value
 
 class SentryTunnelSession(OutgoingSession):
     def __init__(self) -> None:
-        super().__init__(role="sentry_tunnel", timeout=5)
+        super().__init__(role="sentry_tunnel", timeout=1)
 
 
 @csrf_exempt