ADD CORRECTED PATH FOR `extrinsics.mmd`

[zeel991]

This PR corrects the documentation path for the extrinsics.mmd file referenced in unchecked_extrinsics.rs.

The original code was referencing the file path incorrectly. The correct path is now provided as follows:

#[cfg_attr(all(feature = "std", not(windows)), doc = simple_mermaid::mermaid!("../../../../../docs/mermaid/extrinsics.mmd"))]

The file structure for the relevant files is as follows:

substrate-sdk/
├── docs/
│   └── mermaid/
│       └── extrinsics.mmd
└── substrate/
    └── primitives/
        └── runtime/
            └── src/
                └── generic/
                    └── unchecked_extrinsics.rs

• Correct File Location: ../../../../../docs/mermaid/extrinsics.mmd
• Reference Location in Code: substrate-sdk/substrate/primitives/runtime/src/generic/unchecked_extrinsics.rs

This ensures that the documentation will correctly render the Mermaid diagram from the specified location in the code.

[zeel991]

It is a symlink, so should do the same thing. It also renders correctly here: https://docs.rs/sp-runtime/39.0.0/sp_runtime/generic/struct.UncheckedExtrinsic.html

Where does it not render correcty?

Symlinks might not work correctly on Windows due to differences in how symlinks are handled. This could cause issues with rendering the documentation locally.