Update alpine Docker tag to v3.22

| datasource | package | from | to   |
| ---------- | ------- | ---- | ---- |
| docker     | alpine  | 3.21 | 3.22 |


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

Author: renovate[bot]

build/Dockerfile.nginxplus

@@ -14,7 +14,7 @@ RUN apk add --no-cache git make \
     && git checkout 0de3ba3451d8b05cced5eedb744a82db90db7e53 \
     && make build
 
-FROM alpine:3.21
+FROM alpine:3.22
 
 ARG NGINX_PLUS_VERSION=R34
 ARG NJS_DIR