Update BASE_VERSION to 1.27-2025-09-23T19-02-15 (#57765)

Author: istio-testing

Makefile.core.mk

@@ -49,7 +49,7 @@ endif
 export VERSION
 
 # Base version of Istio image to use
-BASE_VERSION ?= 1.27-2025-07-30T19-02-15
+BASE_VERSION ?= 1.27-2025-09-23T19-02-15
 ISTIO_BASE_REGISTRY ?= gcr.io/istio-release
 
 export GO111MODULE ?= on