Update src/aks-preview/HISTORY.rst

Author: FumingZhang

src/aks-preview/HISTORY.rst

@@ -16,6 +16,12 @@ Pending
 
 19.0.0b26
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+19.0.0b26
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+* `az aks create/update`: Add `--enable-app-routing-istio` / `--disable-app-routing-istio` (short: `--enable-ari` / `--disable-ari`) flags to enable or disable Istio as a Gateway API implementation for App Routing.
+* `az aks approuting gateway istio enable/disable`: Add new subcommands to enable or disable the Istio Gateway API implementation for App Routing on an existing cluster.
 * Add 'mTLS' as a transit encryption type option for `--acns-transit-encryption-type` in `az aks create/update`
 
 19.0.0b25