fix: make Prometheus run as root

Following guidance in https://github.com/hassio-addons/addon-prometheus/pull/49#discussion_r926048521.

Tested in local dev container.

prometheus/Dockerfile

@@ -30,7 +30,6 @@ RUN \
     \
     && curl -J -L -o /tmp/prometheus.tar.gz \
         "https://github.com/prometheus/prometheus/releases/download/v${PROMETHEUS_VERSION}/prometheus-${PROMETHEUS_VERSION}.linux-${ARCH}.tar.gz" \
-    && adduser -s /bin/false -D -H prometheus \
     && cd /tmp \
     && tar -xvf /tmp/prometheus.tar.gz \
     && mkdir -p /etc/prometheus \
@@ -39,7 +38,6 @@ RUN \
     && cp -R prometheus-${PROMETHEUS_VERSION}.linux-${ARCH}/console_libraries/ /etc/prometheus/ \
     && cp -R prometheus-${PROMETHEUS_VERSION}.linux-${ARCH}/consoles/ /etc/prometheus/ \
     && rm -r prometheus-${PROMETHEUS_VERSION}.linux-${ARCH} \
-    && chown -R prometheus:prometheus /etc/prometheus \
     && pip3 install \
         --no-cache-dir \
         --prefer-binary \

prometheus/rootfs/etc/services.d/prometheus-configgen/run

@@ -3,11 +3,10 @@ bashio::log.info 'Starting prometheus config generator...'
 
 if ! bashio::fs.directory_exists /share/prometheus/targets; then
   mkdir -p /share/prometheus/targets
-  chown -R prometheus:prometheus /share/prometheus/targets
 fi
 
 cd /opt/prometheus-configgen || bashio::exit.nok \
   "Could not change working directory for prometheus-configgen."
 
 # Run Prometheus
-exec s6-setuidgid prometheus python3 combiner
+exec python3 combiner

prometheus/rootfs/etc/services.d/prometheus/run

@@ -28,18 +28,15 @@ done
 
 if ! bashio::fs.directory_exists /data/prometheus; then
   mkdir -p /data/prometheus
-  chown prometheus:prometheus /data/prometheus
 fi
 
 if ! bashio::fs.directory_exists /share/prometheus/rules; then
   mkdir -p /share/prometheus/rules
-  chown -R prometheus:prometheus /share/prometheus/rules
 fi
 
 if ! bashio::fs.directory_exists /share/prometheus/targets; then
   mkdir -p /share/prometheus/targets
-  chown -R prometheus:prometheus /share/prometheus/targets
 fi
 
 # Run Prometheus
-exec s6-setuidgid prometheus /usr/local/bin/prometheus "${options[@]}"
+exec /usr/local/bin/prometheus "${options[@]}"