fix: docs/Dockerfile to reduce vulnerabilities (#5570)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE321-MUSL-8720634
- https://snyk.io/vuln/SNYK-ALPINE321-OPENSSL-8690014
- https://snyk.io/vuln/SNYK-ALPINE321-OPENSSL-8690014
- https://snyk.io/vuln/SNYK-ALPINE321-OPENSSL-8710358
- https://snyk.io/vuln/SNYK-ALPINE321-OPENSSL-8710358

Signed-off-by: khanhtc1202 <khanhtc1202@gmail.com>
Co-authored-by: snyk-bot <snyk-bot@snyk.io>

Author: khanhtc1202

docs/Dockerfile

@@ -2,7 +2,7 @@ FROM golang:1.22.4-alpine3.20 AS builder
 COPY main.go .
 RUN go build -o /server main.go
 
-FROM alpine:3.21.0
+FROM alpine:3.21.3
 RUN apk --no-cache add ca-certificates
 
 COPY --from=builder /server ./