feat(docs): Update SDMC folder instruction in Azahar guide

[MisterSheeple]

This pr is made in preparation of the release of Azahar 2126.0, which includes an easier way to access the SDMC folder. That feature was added because some people who used the Pretendo Azahar guide were confused by their SDMC folder not being in the default location. When the Azahar guide was first written, I wrote it with the default SDMC location in mind because we thought that the user wouldn't change their SDMC directory unless they know what they're doing, and would therefore know to plug in the location they configured when they get to this part of the guide. Unfortunately, we later found that there are some user configurations where the SDMC directory is not default, but the user themselves did not knowingly change it. The discovered use case was EmuDeck, a simple emulator installer primarily designed for Steam Deck and other PC gaming handhelds. EmuDeck automatically switches the SDMC directory to an external drive (such as the Steam Deck's SD card) when the user configures EmuDeck to load games from an external drive instead of the primary one. This resulted in a scenario where a user had their SDMC directory pointed to their Steam Deck's SD card, and they could not proceed with the installation process because they couldn't find their SDMC folder in its default location. With this new feature being added in Azahar 2126.0, this will alleviate the edge case by giving a button to open a file explorer window in wherever the SDMC folder is, without relying on the user knowing where exactly it is on their system.

Please do not make this edit go live until Azahar 2126.0 is released. This is currently estimated to happen around late July or early August.

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• What I'm implementing was an approved issue.
• I have tested all of my changes.