simplify animated_material example #35501

Job	Run time
build (windows-latest)	4m 8s
check-bevy-internal-imports	4s
check-doc	5m 14s
build (ubuntu-latest)	1m 53s
check-missing-examples-in-docs	29s
build (macos-latest)	2m 24s
ci	1m 37s
miri	6m 38s
run-examples-on-windows-dx12	14m 3s
toml	4s
check-missing-features-in-docs	29s
markdownlint	1m 8s
check-compiles	2m 17s
msrv	58s
build-wasm	40s
	42m 6s

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