change install candidates (py3-pip)

docker/Dockerfile

@@ -4,7 +4,7 @@ RUN mkdir /app && mkdir /config && mkdir /data
 COPY config.py program.py database.py request.py message.py /app/
 VOLUME /data
 
-RUN apk add --no-cache python3 curl \
+RUN apk add --no-cache py3-pip curl \
   && pip3 install --upgrade pip setuptools apprise pyyaml
 
 ENV SUPERCRONIC_URL=https://github.com/aptible/supercronic/releases/download/v0.1.9/supercronic-linux-amd64 \