Fixed webserver workhorse to use the correct values from values.yaml for image

What does this MR do?

Fixes the web server deployment template from pulling in a value block rather then the value itself. Without this fix when using a specific workhorse repository and tag a map is created the image value is invalid.

Related issues

Author checklist

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Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
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• Tests added/updated
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Equivalent MR/issue for Gitlab Operator project opened (see Operator documentation on impact of Charts changes)
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.