Updates sample code and adds note for migrating to Rusoto 0.25.0 and later.
Updates sample code and adds note for migrating to Rusoto 0.25.0 and later.

rusoto/rusoto,DualSpark/rust-aws,DualSpark/rusoto,mattico/rusoto,mattico/rusoto,SecurityInsanity/rusoto,rusoto/rusoto,rusoto/rusoto,DualSpark/rusoto,SecurityInsanity/rusoto,mattico/rusoto,DualSpark/rust-aws,DualSpark/rusoto,DualSpark/rust-aws