Bump alpine from 3.20 to 3.21 (#129)

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]

Diff for: Dockerfile

@@ -13,7 +13,7 @@ COPY . .
 
 RUN cd cmd/vulnerability-db-api/ && GOOS=linux GOARCH=amd64 go build . && cd -
 
-FROM alpine:3.20
+FROM alpine:3.21
 
 RUN apk add --no-cache --update bash gettext