[Release] Update index.json for extension [ aks-preview-18.0.0b21 ]

Triggered by Azure CLI Extensions Release Pipeline - ADO_BUILD_URL: https://dev.azure.com/msazure/One/_build/results?buildId=131951941&view=results

Last commit: ecb6680

Author: azclibot

src/index.json

@@ -14343,6 +14343,49 @@
                     "version": "18.0.0b20"
                 },
                 "sha256Digest": "4bb08e8f87ab5392f4a52510b8bb44e824acc48eec3fa4371ad71acc3bd44d85"
+            },
+            {
+                "downloadUrl": "https://azcliprod.blob.core.windows.net/cli-extensions/aks_preview-18.0.0b21-py2.py3-none-any.whl",
+                "filename": "aks_preview-18.0.0b21-py2.py3-none-any.whl",
+                "metadata": {
+                    "azext.isPreview": true,
+                    "azext.minCliCoreVersion": "2.61.0",
+                    "classifiers": [
+                        "Development Status :: 4 - Beta",
+                        "Intended Audience :: Developers",
+                        "Intended Audience :: System Administrators",
+                        "Programming Language :: Python",
+                        "Programming Language :: Python :: 3",
+                        "Programming Language :: Python :: 3.6",
+                        "Programming Language :: Python :: 3.7",
+                        "Programming Language :: Python :: 3.8",
+                        "License :: OSI Approved :: MIT License"
+                    ],
+                    "extensions": {
+                        "python.details": {
+                            "contacts": [
+                                {
+                                    "email": "azpycli@microsoft.com",
+                                    "name": "Microsoft Corporation",
+                                    "role": "author"
+                                }
+                            ],
+                            "document_names": {
+                                "description": "DESCRIPTION.rst"
+                            },
+                            "project_urls": {
+                                "Home": "https://github.com/Azure/azure-cli-extensions/tree/main/src/aks-preview"
+                            }
+                        }
+                    },
+                    "generator": "bdist_wheel (0.30.0)",
+                    "license": "MIT",
+                    "metadata_version": "2.0",
+                    "name": "aks-preview",
+                    "summary": "Provides a preview for upcoming AKS features",
+                    "version": "18.0.0b21"
+                },
+                "sha256Digest": "982ad4a62453c868ae1f46010cea14af8a55ce51d91f5420715c636c308b0407"
             }
         ],
         "aksarc": [