Don't use blocks for defaults

Rubocop recommends the basic syntax instead, which does make sense.

config/puma.rb

@@ -1,23 +1,25 @@
+# frozen_string_literal: true
+
 # Puma can serve each request in a thread from an internal thread pool.
 # The `threads` method setting takes two numbers: a minimum and maximum.
 # Any libraries that use thread pools should be configured to match
 # the maximum value specified for Puma. Default is set to 5 threads for minimum
 # and maximum; this matches the default thread size of Active Record.
 #
-max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
+max_threads_count = ENV.fetch("RAILS_MAX_THREADS", 5)
 min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
 threads min_threads_count, max_threads_count
 
 # Specifies the `port` that Puma will listen on to receive requests; default is 3000.
 #
-port        ENV.fetch("PORT") { 3000 }
+port        ENV.fetch("PORT", 3000)
 
 # Specifies the `environment` that Puma will run in.
 #
-environment ENV.fetch("RAILS_ENV") { "development" }
+environment ENV.fetch("RAILS_ENV", "development")
 
 # Specifies the `pidfile` that Puma will use.
-pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
+pidfile ENV.fetch("PIDFILE", "tmp/pids/server.pid")
 
 # Specifies the number of `workers` to boot in clustered mode.
 # Workers are forked web server processes. If using threads and workers together