Upgrade to Drupal 9.3, 8 is EOL

Dockerfile

@@ -1,4 +1,4 @@
-FROM drupal:8
+FROM drupal:9.3
 LABEL maintainer="Torben Nehmer <torben@nehmer.net>"
 
 RUN set -ex; \

build-container.sh

@@ -5,5 +5,5 @@ set -ex
 # Required, otherwise package building will fail.
 echo N | sudo tee /sys/module/overlay/parameters/metacopy
 
-docker pull drupal:8
+docker pull drupal:9.3
 docker build --force-rm -t nathan/drupal8 -f Dockerfile build