Make Nvidia even clearer, remove references to "open drivers"

[alexvojproc]

At the moment, our Images page has six tables like this:

secureblue.dev/content/IMAGES.md

Lines 46 to 50 in 7b34d8f

	| Name | Base | NVIDIA Support | ARM64 Support |
	|-------------------------------------------|-----------|-------------------------|------------------------|
	| `silverblue-main-hardened` | Silverblue| No | Beta |
	| `silverblue-nvidia-hardened` | Silverblue| Yes, closed drivers | No |
	| `silverblue-nvidia-open-hardened` | Silverblue| Yes, open drivers | No |

When users are selecting the right image to download, I think a common point of confusion is between nvidia-open and Nouveau (in main). Nvidia-open are not open drivers (as far as I'm aware), but rather just the kernel module is open, and the userspace drivers remain closed-source. These are the recommended drivers for new Nvidia hardware. Nouveau drivers integrate with the rest of the Mesa stack, but have performance and power management issues.

I wonder whether something like this would be better:

Name	Base	NVIDIA Support	ARM64 Support
silverblue-main-hardened	Silverblue	Poor (Nouveau)	Beta
silverblue-nvidia-hardened	Silverblue	Yes, legacy closed module	No
silverblue-nvidia-open-hardened	Silverblue	Yes, modern open module	No

I know the Nvidia drop-down box says "No", "Yes (pre-Turing)" and "Yes (Turing and later)", but it might be hard to see how this maps to the Images page. Similarly, the download note refers to nvidia and nvidia-open, which isn't what appears in the drop-down box.

secureblue.dev/content/INSTALL.md

Line 80 in 7b34d8f

{% include alert.html type='note' content='<b>nvidia-open</b> images are recommended for systems with NVIDIA GPUs Turing or newer (GTX 16XX+, RTX 20XX+). Consult <a href="https://nouveau.freedesktop.org/CodeNames.html">this page</a> if you&#39;re not sure what family your GPU belongs to. These include the new <a href="https://github.com/NVIDIA/open-gpu-kernel-modules">open kernel modules</a> from NVIDIA, not Nouveau. <b>nvidia</b> images are recommended for systems with NVIDIA GPUs Pascal or older. These include the closed kernel modules from NVIDIA.' %}