[Genesis Plus GX] Pixel aspect ratio not accounted for in "Use system's recommendation" Display config

[badgertapes]

When "Use system's recommendation" is enabled, all Genesis Plus GX games still display in a 1:1 pixel aspect ratio, regardless of system or region setting. Forcing the games to run at 4:3 under "Use custom AR" provides a good enough facsimile, though I have to manually disable it for when I play games using other systems and cores. The libretro docs website lists aspect ratio options under Core-Provided Aspect Ratio [genesis_plus_gx_aspect_ratio]

2.10 dev at e56830549