docker: Upgrade docker-postgresql to 14.

Because we have no upgrade path for the data in the PostgreSQL
databases themselves, this is pushed as, e.g.,
`zulip/zulip-postgresql:14` and *not* as
`zulip/zulip-postgresql:latest`.

Fixes: zulip#21211

Co-authored-by: Alex Vandiver <alexmv@zulip.com>

Dockerfile-postgresql

@@ -5,9 +5,13 @@
 # the on-disk data in volumes. So the base image can not currently be upgraded
 # without users needing a manual pgdump and restore.
 
+# https://hub.docker.com/r/groonga/pgroonga/tags
+ARG PGROONGA_VERSION=latest
+ARG POSTGRESQL_VERSION=14
+FROM groonga/pgroonga:$PGROONGA_VERSION-alpine-$POSTGRESQL_VERSION-slim
+
 # Install hunspell, Zulip stop words, and run Zulip database
 # init.
-FROM groonga/pgroonga:latest-alpine-10-slim
 RUN apk add -U --no-cache hunspell-en
 RUN ln -sf /usr/share/hunspell/en_US.dic /usr/local/share/postgresql/tsearch_data/en_us.dict && ln -sf /usr/share/hunspell/en_US.aff /usr/local/share/postgresql/tsearch_data/en_us.affix
 COPY puppet/zulip/files/postgresql/zulip_english.stop /usr/local/share/postgresql/tsearch_data/zulip_english.stop