Bump rspec_rails test project to Rails 7.2.3.1

Pin rails = 7.2.3.1 and bump puma to ~> 6.0 (Puma 5 is incompatible
with Rack 3, which Rails 7.2 pulls in). Switch load_defaults to 7.2
and replace the now-removed boolean form of show_exceptions with :none.

Author: sferik

test_projects/rails/rspec_rails/Gemfile

@@ -15,9 +15,9 @@ else
 end
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
-gem "rails", "~> 6.1.0"
+gem "rails", "= 7.2.3.1"
 # Use Puma as the app server
-gem "puma", "~> 5.0"
+gem "puma", "~> 6.0"
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
 gem "jbuilder", "~> 2.7"
 # Use Active Model has_secure_password