Corrected parameter description for handle_dup_keys in the pipline ru…

[kodjo-anipah]

Description

Corrected parameter description for handle_dup_keys in the pipeline rule key_value function. If not specified, the function defaults to using the first encountered value for duplicate keys.

Motivation and Context

resolves #17892

How Has This Been Tested?

Locally Create a rule and add it to a pipeline:

rule "Test keys_array"
when
  true
then
  let output_1 = get_field(
    field : "message"
  );
  let output_2 = to_string(
    value : output_1
  );
  let output_3 = key_value(
    value : output_2,
    ignore_empty_values : true,
    allow_dup_keys : true,
    handle_dup_keys : "array"
  );
  set_fields(
    fields : output_3
  );
end

send in following example message via gelf input:

curl -X POST -H "Content-Type: application/json" -d '{"version": "1.1", "host": "example.com", "short_message": "test=1 test=2 test2=3", "facility": "gelf-test"}' http://localhost:12201/gelf

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[moesterheld]

I like the new default parameter in the rule builder. Thanks for adding that.
Changes LGTM, but please change the PR description as the array parameter value has been removed from the pr again due to having no additional value.