Update dependency alpine to v3.15

Author: renovate-bot

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.13@sha256:69e70a79f2d41ab5d637de98c1e0b055206ba40a8145e7bddb55ccc04e13cf8f AS builder
+FROM alpine:3.15@sha256:4edbd2beb5f78b1014028f4fbb99f3237d9561100b6881aabbf5acce2c4f9454 AS builder
 
 ENV GIT_CRYPT_VERSION 0.6.0
 ENV GIT_CRYPT_CHECKSUM 777c0c7aadbbc758b69aff1339ca61697011ef7b92f1d1ee9518a8ee7702bb78
@@ -17,7 +17,7 @@ RUN curl -fSsL https://github.com/AGWA/git-crypt/archive/$GIT_CRYPT_VERSION.tar.
     && make \
     && make install PREFIX=/usr
 
-FROM alpine:3.13@sha256:69e70a79f2d41ab5d637de98c1e0b055206ba40a8145e7bddb55ccc04e13cf8f
+FROM alpine:3.15@sha256:4edbd2beb5f78b1014028f4fbb99f3237d9561100b6881aabbf5acce2c4f9454
 
 RUN apk --update --no-cache add \
     git \