Update alpine Docker tag to v3.20

Author: renovate[bot]

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.13@sha256:d0710affa17fad5f466a70159cc458227bd25d4afb39514ef662ead3e6c99515 AS builder
+FROM alpine:3.20@sha256:e72ad0747b9dc266fca31fb004580d316b6ae5b0fdbbb65f17bbe371a5b24cff AS builder
 
 ENV GIT_CRYPT_VERSION 0.7.0
 ENV GIT_CRYPT_CHECKSUM 2210a89588169ae9a54988c7fdd9717333f0c6053ff704d335631a387bd3bcff
@@ -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:d0710affa17fad5f466a70159cc458227bd25d4afb39514ef662ead3e6c99515
+FROM alpine:3.20@sha256:e72ad0747b9dc266fca31fb004580d316b6ae5b0fdbbb65f17bbe371a5b24cff
 
 RUN apk --update --no-cache add \
     git \