Removed headers filter from loopbackApi

[Junjiequan]

Description

For better compatibility, visibility, and ease of use headers filter are removed and will no longer be supported by scicat backend

Motivation

Couple of reasons to remove header filters as following:

• Limited Visibility and Debugging: Headers are less visible than query parameters or request bodies, complicating debugging and logging.
• Convention and Consistency: In RESTful APIs, headers are conventionally used for control-related metadata like content type or authentication, not for business logic like filter parameters. Using them for filters goes against standard practices.
• Security Concerns: Using headers for business logic can expose APIs to overlooked security vulnerabilities.

Tests included/Docs Updated?

• [ ] Included for each change/fix?
• [ ] Passing? (Merge will not be approved unless this is checked)
• [ ] Docs updated?
• [ ] New packages used/requires npm install?
• [ ] Toggle added for new features?
• [ ] Requires update of SciCat backend API?