Remove Spring from the project

IMHO, Spring no longer provides benefits in this project and:

- Spring was already disabled in the test environment since commit e4e0cb5d47
- Rails removed Spring as a default installation option in 2021 [1]

[1] PR #42997 from https://github.com/rails/rails/

Gemfile

@@ -109,7 +109,6 @@ group :development do
   gem "rubocop-rspec", "~> 3.4.0", require: false
   gem "rubocop-rspec_rails", "~> 2.30.0", require: false
   gem "rvm1-capistrano3", "~> 1.4.0", require: false
-  gem "spring", "~> 4.2.1"
   gem "web-console", "~> 4.2.1"
 end
 

Gemfile.lock

@@ -661,7 +661,6 @@ GEM
       version_gem (>= 1.1.8, < 3)
     social-share-button (1.2.4)
       coffee-rails
-    spring (4.2.1)
     sprockets (4.2.1)
       concurrent-ruby (~> 1.0)
       rack (>= 2.2.4, < 4)
@@ -826,7 +825,6 @@ DEPENDENCIES
   simplecov-lcov (~> 0.8.0)
   sitemap_generator (~> 6.3.0)
   social-share-button (~> 1.2.4)
-  spring (~> 4.2.1)
   sprockets (~> 4.2.1)
   sprockets-rails (~> 3.5.2)
   turbolinks (~> 5.2.1)

bin/spring

@@ -1,17 +0,0 @@
-#!/usr/bin/env ruby
-
-# This file loads spring without using Bundler, in order to be fast.
-# It gets overwritten when you run the `spring binstub` command.
-
-unless defined?(Spring)
-  require "rubygems"
-  require "bundler"
-
-  lockfile = Bundler::LockfileParser.new(Bundler.default_lockfile.read)
-  spring = lockfile.specs.find { |spec| spec.name == "spring" }
-  if spring
-    Gem.use_paths Gem.dir, Bundler.bundle_path.to_s, *Gem.path
-    gem "spring", spring.version
-    require "spring/binstub"
-  end
-end

config/spring.rb

@@ -1,6 +0,0 @@
-%w[
-  .ruby-version
-  .rbenv-vars
-  tmp/restart.txt
-  tmp/caching-dev.txt
-].each { |path| Spring.watch(path) }