fix(chart-readme): Use correct indentation in lifecyce examples

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Proposed changes

Problem: The Helm chart example configuration for configuring lifecycle.preStop uses a misleading indentation that can confuse users.

Solution: Updated the Helm chart's README by fixing the indentation of the example code block to showcase the proper JSON paths of nginxGateway.lifecycle.preStop.exec.command and nginx.lifecycle.preStop.exec.command. The PreStop hook is described as having exec as a handler in https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#hook-handler-execution and https://kubernetes.io/docs/tasks/configure-pod-container/attach-handler-lifecycle-event/#define-poststart-and-prestop-handlers.

Testing:

Successfully deployed this chart into my cluster with the updated paths:

› kubectl -n nginx-gateway get pod -o json | jq '.items[].spec.containers[] | {name, lifecycle}'
{
  "name": "nginx-gateway",
  "lifecycle": {
    "preStop": {
      "exec": {
        "command": [
          "/usr/bin/gateway",
          "sleep",
          "--duration=30s"
        ]
      }
    }
  }
}
{
  "name": "nginx",
  "lifecycle": {
    "preStop": {
      "exec": {
        "command": [
          "/bin/sh",
          "-c",
          "/bin/sleep 30"
        ]
      }
    }
  }
}

• make unit-test
• make lint
• make lint-helm
• make generate-all
• kubectl -n nginx-gateway exec deployment/gateway-nginx-gateway-fabric -c nginx -- nginx -T

make unit-test looks like everything passed except this single failure at the end:

PASS
coverage: 57.7% of statements
composite coverage: 93.6% of statements

Ginkgo ran 27 suites in 56.33843625s

There were failures detected in the following suites:
  static ./internal/mode/static

Test Suite Failed
exit status 1
gmake: *** [Makefile:196: unit-test] Error 1

Checklist

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

NONE

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