fixing line comment in 2d_shapes.rs example #40068

Job	Run time
build (windows-latest)	4m 16s
ci	1m 46s
check-bevy-internal-imports	5s
build (ubuntu-latest)	2m 5s
build (macos-latest)	3m 25s
check-cfg	56s
check-doc	7m 40s
check-missing-examples-in-docs	30s
miri	6m 39s
run-examples-macos-metal	4m 58s
toml	2m 6s
typos	6s
check-missing-features-in-docs	32s
markdownlint	1m 14s
check-compiles	3m 6s
msrv	48s
build-wasm	39s
build-wasm-atomics	1m 10s
	42m 1s

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