the custom-config.toml configmap content is not getting updated fully in config.toml file of gitlab-runner pod

Here I am using below custom-config.toml file to append the custom volume settings in gitlab-runner pod

the content of custom-config.toml file

[[runners]]
  [runners.kubernetes]
    [runners.kubernetes.volumes]
      [[runners.kubernetes.volumes.host_path]]
        name = "docker"
        mount_path = "/var/run/docker.sock"
        read_only = false
      [[runners.kubernetes.volumes.host_path]]
        name = "buildah"
        mount_path = "/var/lib/containers/"
        read_only = false

then I use below gitlab-runner crd file

apiVersion: apps.gitlab.com/v1beta2
kind: Runner
metadata:
  name: gitlab-runner
spec:
  gitlabUrl: https://gitlab.com/
  buildImage: alpine
  token: gitlab-runner-secret
  config: custom-config-toml
  tags: openshift, test-runner

I created secret, crd using the documentation https://docs.gitlab.com/runner/install/openshift.html

gitlab-runner pod started successfully and its in running state.

but during the execution CI/CD job I am getting below error

$ buildah bud --cache-from ${IMAGE}:${TAG} -t ${IMAGE}:${TAG} $DOCKERFILE
error opening "/var/lib/containers/storage/storage.lock": permission denied

When I checked the config.toml file of gitlab-runner pod found that read_only = false property is not getting updated in config.toml file

the content of config.toml file of gitlab-runner pod

listen_address = "[::]:9252"
concurrent = 10
check_interval = 30
log_level = "info"

[session_server]
  session_timeout = 1800

[[runners]]
  name = "gitlab-runner-runner-xxxx"
  output_limit = 4096
  request_concurrency = 1
  url = "https://gitlab.com"
  token = "xxxx"
  executor = "kubernetes"
  [runners.custom_build_dir]
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]
    [runners.cache.azure]
  [runners.kubernetes]
    host = ""
    bearer_token_overwrite_allowed = false
    image = "alpine"
    namespace = "test"
    namespace_overwrite_allowed = ""
    privileged = false
    helper_image = "registry.connect.redhat.com/gitlab/gitlab-runner-helper@sha256:3e6842e5a68b1eb561ce218eae09dc1a37b2eab2a36d7e96ceab327c667d41a9"
    poll_timeout = 180
    service_account_overwrite_allowed = ""
    pod_annotations_overwrite_allowed = ""
    [runners.kubernetes.affinity]
    [runners.kubernetes.pod_security_context]
    [runners.kubernetes.volumes]

      [[runners.kubernetes.volumes.host_path]]
        name = "docker"
        mount_path = "/var/run/docker.sock"

      [[runners.kubernetes.volumes.host_path]]
        name = "buildah"
        mount_path = "/var/lib/containers/"
    [runners.kubernetes.dns_config]