visualc: Remove obsolete reference to mojoshader_metal.c #834

Job	Run time
Fedora Linux MinGW (SDL2)	1m 9s
FreeBSD (SDL2)	1m 3s
Steam Linux Runtime (SDL2)	1m 17s
iOS/tvOS (SDL3) (iOS, iphoneos, arm64)	55s
Fedora Linux MinGW (SDL3)	59s
Debian Linux PPC (SDL2)	1m 45s
Debian Linux PPC (SDL3)	58s
Steam Linux Runtime (SDL3)	1m 19s
iOS/tvOS (SDL3) (iOS, iphonesimulator, x86_64;arm64)	59s
iOS/tvOS (SDL3) (tvOS, appletvos, arm64)	54s
macOS (x86_64) (SDL2)	39s
iOS/tvOS (SDL3) (tvOS, appletvsimulator, x86_64;arm64)	1m 3s
macOS (Universal) (SDL3)	1m 20s
Windows MSVC (SDL2)	1m 9s
Windows MSVC (SDL3)	1m 0s
	16m 29s

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