Remove unused ArrayRef::is_arrow #5628

Job	Run time
check-java-publish-build (aarch64-unknown-linux-gnu, runs-on=29785010032/runner=arm64-medium/imag...	53s
Python (wheel build)	6m 15s
Rust publish dry-run	48s
check-java-publish-build (x86_64-unknown-linux-gnu, runs-on=29785010032/runner=amd64-medium/image...	48s
Compat check / compat-test	37s
	9m 21s

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