Validate/Remove trailing slash in host name

Created a Merge Request:
https://git.drupalcode.org/project/ai_provider_litellm/-/merge_requests/9

I tested this locally and the fix appears to work. I now get an error message indicating I should not have a trailing slash. Setting to RTBC.

Thanks, merged MR and credited everyone using the new Contribution Record system
https://new.drupal.org/contribution-record/11415156

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