[Kaniko] Bump kaniko for open source [1.6.x] (#5298)

mlrun/config.py

@@ -444,7 +444,7 @@
             # pip install <requirement_specifier>, e.g. mlrun==0.5.4, mlrun~=0.5,
             # git+https://github.com/mlrun/mlrun@development. by default uses the version
             "mlrun_version_specifier": "",
-            "kaniko_image": "gcr.io/kaniko-project/executor:v1.8.0",  # kaniko builder image
+            "kaniko_image": "gcr.io/kaniko-project/executor:v1.21.1",  # kaniko builder image
             "kaniko_init_container_image": "alpine:3.18",
             # image for kaniko init container when docker registry is ECR
             "kaniko_aws_cli_image": "amazon/aws-cli:2.7.10",