chore(deps): update docker.io/library/alpine docker tag to v3.21.0 (#436)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -52,7 +52,7 @@ RUN --mount=type=cache,target=/root/.cache/go-build CGO_ENABLED=0 GOOS=${TARGETO
   -X ${PACKAGE}/internal/version.BuildTimestamp=${BUILD_TIMESTAMP}" \
   -o bin/burrito main.go
 
-FROM docker.io/library/alpine:3.20.3@sha256:1e42bbe2508154c9126d48c2b8a75420c3544343bf86fd041fb7527e017a4b4a
+FROM docker.io/library/alpine:3.21.0@sha256:21dc6063fd678b478f57c0e13f47560d0ea4eeba26dfc947b2a4f81f686b9f45
 
 WORKDIR /home/burrito