Remove the 'de_dot' functionality as it is depricated

[bodz1lla]

The 'de_dot' functionality is depricated and will be removed from the fluent-plugin-kubernetes_metadata_filter as it was mentioned below in the release_notes.md.

Found the warning in splunk-logging pods.

2024-01-04 19:35:09 +0000 [info]: init supervisor logger path=nil rotate_age=nil rotate_size=nil
2024-01-04 19:35:10 +0000 [INFO]: Reading bearer token from /var/run/secrets/kubernetes.io/serviceaccount/token
2024-01-04 19:35:11 +0000 [info]: #0 init worker0 logger path=nil rotate_age=nil rotate_size=nil
2024-01-04 19:35:11 +0000 [INFO]: Reading bearer token from /var/run/secrets/kubernetes.io/serviceaccount/token
2024-01-04 19:35:11 +0000 [warn]: parameter 'de_dot' in <filter k8s.**>
  @type kubernetes_metadata
  annotation_match [".*"]
  de_dot false
  watch true
  cache_ttl 3600
</filter> is not used.

Review plugin release notes.

fluent-plugin-kubernetes_metadata_filter-3.1.0 $ grep de_dot release_notes.md
As of this release, the 'de_dot' functionality is depricated and will be removed in future releases.

Environment:

Splunk-connect 1.5.3
Fluentd 1.15.3
fluent-plugin-kubernetes_metadata_filter 3.1.0