Drop Coppelia sim backend

[oxkitsune]

This also checks the Cargo.lock file in? It wasn't for some reason.

[Copilot]

Pull Request Overview

This PR removes the CoppeliaSim backend from the project and updates related documentation, error handling, module usage, and dependency management.

• Removed CoppeliaSim backend documentation and code from the library.
• Removed error variants and module exports related to CoppeliaSim.
• Updated Cargo.toml to drop the CoppeliaSim dependency and bump the package version.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
nidhogg/src/lib.rs	Documentation update: removed CoppeliaSim backend entry from the supported backends table.
nidhogg/src/error.rs	Removed the CoppeliaConnectError error variant.
nidhogg/src/backend/mod.rs	Removed module import and public re-export for CoppeliaSim.
nidhogg/src/backend/coppelia.rs	Removed the entire file implementing the CoppeliaSim backend.
nidhogg/examples/generic_backend.rs	Removed commented instantiation of the CoppeliaSim backend.
nidhogg/Cargo.toml	Dropped the CoppeliaSim dependency and updated the version to 0.7.0.

[YukumoHunter]

😭