update release notes

Signed-off-by: Karol Szwaj <karol.szwaj@gmail.com>

Author: cnvergence

release-notes/v1.7.3.yaml

@@ -1,4 +1,4 @@
-date: April 28, 2026
+date: May 8, 2026
 
 # Changes that are expected to cause an incompatibility with previous versions, such as deletions or modifications to existing APIs.
 breaking changes: |
@@ -17,6 +17,7 @@ bug fixes: |
   Fixed `ws` and `wss` Backend appProtocols to force HTTP/1.1 upstream connections instead of negotiating HTTP/2, avoiding compatibility issues with WebSocket backends that do not support RFC 8441 extended CONNECT.
   Fixed status conditions not being updated when a route is rejected due to multiple errors.
   Fixed benchmark JSON report emitting `0` for p99 and p999 percentiles by using the nearest Nighthawk histogram percentiles.
+  Fixed active HTTP health checks to use Backend endpoint hostnames before falling back to the effective Route hostname.
 
 # Enhancements that improve performance.
 performance improvements: |