Bump alpine from 3.20 to 3.21 (#184)

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

Author: dependabot[bot]

Dockerfile

@@ -16,7 +16,7 @@ ARG TARGETOS TARGETARCH
 WORKDIR /app/cmd/vulcan-scan-engine
 RUN GOOS=$TARGETOS GOARCH=$TARGETARCH go build .
 
-FROM alpine:3.20
+FROM alpine:3.21
 
 WORKDIR /flyway