build(deps): bump alpine from 3.20 to 3.21 (#1265)

Bumps alpine from 3.20 to 3.21.

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

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

Dockerfile

@@ -42,7 +42,7 @@ COPY . .
 RUN make static
 
 # assemble final container
-FROM alpine:3.20
+FROM alpine:3.21
 RUN apk add --no-cache coreutils diffutils less git openssh-client && \
     apk upgrade --quiet
 COPY --from=build /app/tk /usr/local/bin/tk