Fix: Pass AllowedHandlebarsHelpers configuration to Handlebars.Net.Helpers library

[samlatham]

Bug: The HandlebarsSettings.AllowedHandlebarsHelpers configuration is ignored when trying to enable the Environment helper as documented here https://github.com/wiremock/WireMock.Net?tab=readme-ov-file#handlebarsnet-environment-helper

Repro steps can be found in the associated bug 1415

Fix: This PR is a one line change which passes the AllowedHandlebarsHelpers configuration to Handlebars.Net.Helpers so that optional handlebars helpers can be enabled.

References

#1415
#1410

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