Fix casing in Dockerfile

Change-Id: Ib0249b3ea7f3c059ba7c3763f48a07455a7d3b6a
diff --git a/Dockerfile b/Dockerfile
index 3878b44..2b138d1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 # Use alpine linux as base image
-FROM openjdk:19-alpine as builder
+FROM openjdk:19-alpine AS builder
 
 # Copy repository respecting .dockerignore
 COPY . /kustvakt