simplify match arm
simplify match arm

Signed-off-by: Yi Wu <bc6ae85de42d744f2dc8adc7731d42b35611b18f@pingcap.com>

DualSpark/rusoto,DualSpark/rust-aws,DualSpark/rust-aws,rusoto/rusoto,DualSpark/rusoto,DualSpark/rust-aws,rusoto/rusoto,DualSpark/rusoto,rusoto/rusoto