message: docs: clarify upstream_rq_pending_failure_eject stat
diff: @@ -63,8 +63,8 @@ Every cluster has a statistics tree rooted at *cluster.<name>.* with the followi
  upstream_rq_total, Counter, Total requests
  upstream_rq_active, Gauge, Total active requests
  upstream_rq_pending_total, Counter, Total requests pending a connection pool connection
  - upstream_rq_pending_overflow, Counter, Total requests that overflowed connection pool circuit breaking and were failed
  - upstream_rq_pending_failure_eject, Counter, Total requests that were failed due to a connection pool connection failure
  + upstream_rq_pending_overflow, Counter, Total requests that overflowed connection pool or requests (mainly for HTTP/2) circuit breaking and were failed
  + upstream_rq_pending_failure_eject, Counter, Total requests that were failed due to a connection pool connection failure or remote connection termination
  upstream_rq_pending_active, Gauge, Total active requests pending a connection pool connection
  upstream_rq_cancelled, Counter, Total requests cancelled before obtaining a connection pool connection
  upstream_rq_maintenance_mode, Counter, Total requests that resulted in an immediate 503 due to :ref:`maintenance mode<config_http_filters_router_runtime_maintenance_mode>`
  