[examples] fix minor clippy warnings (#389)

16 jobs for master in 58 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Check
canceled #492790
linux-docker
check-std

00:00:58

canceled #492791
linux-docker
check-wasm

00:00:58

 
  Workspace
canceled #492792
linux-docker
build-std

canceled #492793
linux-docker
build-wasm

canceled #492796
linux-docker
clippy-std

canceled #492797
linux-docker
clippy-wasm

canceled #492795
linux-docker
codecov

canceled #492798
linux-docker
fmt

canceled #492794
linux-docker
test

 
  Examples
canceled #492801
linux-docker
examples-clippy-std

canceled #492802
linux-docker
examples-clippy-wasm

canceled #492803
linux-docker
examples-contract-build

canceled #492800
linux-docker
examples-fmt

canceled #492804
linux-docker
examples-generate-metadata

canceled #492799
linux-docker
examples-test

 
  Publish
canceled #492805
linux-docker
publish-docs