Remove manual fence synchronization #755

Job	Run time
Rocky Linux	1m 44s
Rocky Linux MinGW	1m 18s
FreeBSD	1m 11s
iOS/tvOS SDL3 (iOS, iphoneos, arm64)	45s
iOS/tvOS SDL3 (iOS, iphonesimulator, x86_64;arm64)	50s
Rocky Linux MinGW SDL3	1m 4s
iOS/tvOS SDL3 (tvOS, appletvos, arm64)	45s
Debian Linux PPC	1m 50s
iOS/tvOS SDL3 (tvOS, appletvsimulator, x86_64;arm64)	51s
Debian Linux PPC SDL3	1m 2s
Rocky Linux SDL3	1m 30s
macOS (x86_64)	57s
Windows (MSVC)	1m 8s
macOS (Universal) SDL3	59s
	15m 54s

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