Docs: The Secure Boot Setup page is not compatible with many MSI Laptops

The current MSI BIOS instructions provided in the [CachyOS Secure Boot setup guide](https://wiki.cachyos.org/configuration/secure_boot_setup/) do not apply to many MSI Laptop models. To enable **Setup Mode** on MSI Laptops, users first need to unlock the hidden advanced BIOS settings using a specific key combination.

Without unlocking this menu, the required Secure Boot customization options are not visible.

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### Solution / Steps for MSI Laptops
To successfully enter **Setup Mode** on an MSI Laptop, the following steps must be followed:
1. **Unlock the Advanced/Hidden BIOS:**
* Enter the BIOS screen normally.
* Press the hidden key combination depending on your keyboard layout:
* **Standard Keyboards:** `Right CTRL` + `Right Shift` + `Left ALT` + `F2`
* **Keyboards with Copilot Key:** `Right Copilot Button` + `Right Shift` + `Left ALT` + `F2` [More Info](https://www.reddit.com/r/MSILaptops/comments/boe9uu/unlocking_bios_on_most_msi_laptops/)

2. **Configure Secure Boot:**
* Navigate to **Security** > **Secure Boot**.
* Change **Secure Boot Mode** to `Custom`.
* Select **Reset to Setup Mode** (or *Clear Secure Boot Keys* depending on the exact firmware version).
* Confirm the prompt.
* Press `F10` to save changes and reboot.

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### Context / Additional Info
> **Note:** Many modern MSI laptops shipped recently feature the Copilot key instead of the traditional Right CTRL, which changes the required shortcut to unlock the advanced menu. Updating the CachyOS Wiki or the installer guidance with this information will prevent confusion for MSI laptop users trying to set up Secure Boot.

Open the linked CachyOS Secure Boot setup guide and locate its MSI BIOS instructions. Add the advanced-BIOS shortcut and Setup Mode steps described in the issue, including the Copilot-key variant, then verify the page covers the listed firmware-menu alternatives.

Written by the indexing model from the issue text.