Update alpine Docker tag to v3.22

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.15 as builder
+FROM alpine:3.22 as builder
 
 ENV TINYPROXY_VERSION=1.11.0
 
@@ -18,7 +18,7 @@ RUN adduser -D -u 2000 -h /var/run/tinyproxy -s /sbin/nologin tinyproxy tinyprox
   && make \
   && make install
 
-FROM alpine:3.15
+FROM alpine:3.22
 
 RUN set -xe \
     && apk add --no-cache wget curl bash openssh