chore: update alpine base image to 3.15

Mikołaj Świątek · Mikołaj Świątek · commit f6ed1e9c4981 · 2022-01-11T11:27:38.000Z
diff --git a/Dockerfile b/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:3.13
+FROM alpine:3.15
 
 ENV TERRAFORM_VERSION=0.13.7
 ARG TARGETPLATFORM
