Update front-door-health-probes.md

If health probes fail for every backend in a backend pool, then Front Door considers all backends unhealthy and routes traffic in a round robin distribution across all of them.

Once any backend returns to a healthy state, then Front Door will resume the normal load-balancing algorithm. <--- this originally read "considers all backends healthy" which makes no sense in a failed state

Author: blackthirteen

articles/frontdoor/front-door-health-probes.md

@@ -63,7 +63,7 @@ Azure Front Door uses the same three-step process below across all algorithms to
 
 ## Complete health probe failure
 
-If health probes fail for every backend in a backend pool, then Front Door considers all backends healthy and routes traffic in a round robin distribution across all of them.
+If health probes fail for every backend in a backend pool, then Front Door considers all backends unhealthy and routes traffic in a round robin distribution across all of them.
 
 Once any backend returns to a healthy state, then Front Door will resume the normal load-balancing algorithm.