ci: remove unused Dockerfile

This was used by CI, which is disabled on this branch.

Removing to prevent useless auto-updates by renovate.

Dockerfile

@@ -1,21 +0,0 @@
-# PostgREST Docker Hub image for aarch64.
-# The x86-64 is a single-static-binary image built via Nix, see:
-# nix/tools/docker/README.md
-
-FROM ubuntu:noble@sha256:d1e2e92c075e5ca139d51a140fff46f84315c0fdce203eab2807c7e495eff4f9 AS postgrest
-
-RUN apt-get update -y \
-    && apt install -y --no-install-recommends libpq-dev zlib1g-dev jq gcc libnuma-dev \
-    && apt-get clean \
-    && rm -rf /var/lib/apt/lists/*
-
-COPY postgrest /usr/bin/postgrest
-RUN chmod +x /usr/bin/postgrest
-
-EXPOSE 3000
-
-USER 1000
-
-# Use the array form to avoid running the command using bash, which does not handle `SIGTERM` properly. 
-# See https://docs.docker.com/compose/faq/#why-do-my-services-take-10-seconds-to-recreate-or-stop 
-CMD ["postgrest"]