build(deps): bump alpine from 3.15.2 to 3.16.0 (#268)

Bumps alpine from 3.15.2 to 3.16.0.

---
updated-dependencies:
- dependency-name: alpine
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

heroku.dockerfile

@@ -8,7 +8,7 @@ COPY --chown=rust:rust . ./
 RUN cargo build --release --locked
 
 
-FROM alpine:3.15.2
+FROM alpine:3.16.0
 LABEL maintainer="Ryo Ota <nwtgck@nwtgck.org>"
 
 # Copy executable