uppercase AS in Dockerfile

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.9-slim-buster as builder
+FROM python:3.9-slim-buster AS builder
 ENV PYTHONUNBUFFERED 1
 COPY . ./
 
@@ -7,7 +7,7 @@ ENV POETRY_VERSION=1.3.1
 RUN pip install "poetry==$POETRY_VERSION"
 RUN poetry export --without-hashes > requirements.txt
 
-FROM python:3.9-slim-buster as server
+FROM python:3.9-slim-buster AS server
 
 WORKDIR /app
 COPY . ./