mirror: Fix lint error in Dockerfile (case on "as" keyword)

We get the following lint warning on GitHub Pull Requests:

    The 'as' keyword should match the case of the 'from' keyword

    FromAsCasing: 'as' and 'FROM' keywords' casing do not match
    More info: https://docs.docker.com/go/dockerfile/rule/from-as-casing/

Let's fix it.

Signed-off-by: Quentin Monnet <[email protected]>

Author: qmonnet

Dockerfile

@@ -5,7 +5,7 @@
 
 # hadolint global ignore=DL3008
 
-FROM ubuntu:22.04 as builder
+FROM ubuntu:22.04 AS builder
 
 RUN \
 	export DEBIAN_FRONTEND=noninteractive && \