remove gltf loader async changes #295

Job	Run time
build (windows-latest)	5m 40s
check-bevy-internal-imports	5s
build (ubuntu-latest)	3m 6s
check-cfg	1m 55s
check-doc	9m 32s
build (macos-latest)	3m 28s
check-missing-examples-in-docs	31s
miri	7m 18s
ci	2m 36s
run-examples-macos-metal	4m 56s
toml	2m 8s
typos	6s
check-missing-features-in-docs	0s
markdownlint	1m 6s
check-compiles	0s
msrv	1m 11s
build-wasm-atomics	1m 19s
build-wasm	55s
	45m 52s

Provide feedback