Update puma config to avoid PID files

[ajtucker]

Since Rails 7.2, though not apparently documented, the default when running Rails in production is not to use PID files. See rails/rails@06d614a for a brief description of the changes to puba.rb. The template for this file should be merged in to our production Rails services.

lr-landing/config/puma.rb

Line 22 in fdce08f

pidfile ENV.fetch('PIDFILE', 'tmp/pids/server.pid')

should be:

pidfile ENV["PIDFILE"] if ENV["PIDFILE"]

Note that as part of updating the Dockerfile, we should also update the entrypoint.sh script: https://github.com/epimorphics/lr-landing/blob/dev/entrypoint.sh#L5-L6

[ajtucker]

See also #68