Fix pre Rails 7.1 tests

Refer to rails/rails#54264 (comment)

Author: Bilka2

Appraisals

@@ -23,18 +23,21 @@ end
 appraise "activerecord-6-0" do
   gem "activerecord", "~> 6.0.0"
   gem "sqlite3", "~> 1.4"
+  gem "concurrent-ruby", "< 1.3.5"
 end
 
 appraise "activerecord-6-1" do
   gem "activerecord", "~> 6.1.0"
   gem "sqlite3", "~> 1.4"
   gem "rspec-rails", "~> 4.0"
+  gem "concurrent-ruby", "< 1.3.5"
 end
 
 appraise "activerecord-7-0" do
   gem "activerecord", "~> 7.0.0"
   gem "sqlite3", "~> 1.4"
   gem "rspec-rails", "~> 5.0"
+  gem "concurrent-ruby", "< 1.3.5"
 end
 
 appraise "activerecord-7-1" do

gemfiles/activerecord_6_0.gemfile

@@ -4,5 +4,6 @@ source "https://rubygems.org"
 
 gem "activerecord", "~> 6.0.0"
 gem "sqlite3", "~> 1.4"
+gem "concurrent-ruby", "< 1.3.5"
 
 gemspec path: "../"

gemfiles/activerecord_6_1.gemfile

@@ -5,5 +5,6 @@ source "https://rubygems.org"
 gem "activerecord", "~> 6.1.0"
 gem "sqlite3", "~> 1.4"
 gem "rspec-rails", "~> 6.0"
+gem "concurrent-ruby", "< 1.3.5"
 
 gemspec path: "../"

gemfiles/activerecord_7_0.gemfile

@@ -5,5 +5,6 @@ source "https://rubygems.org"
 gem "activerecord", "~> 7.0.0"
 gem "sqlite3", "~> 1.4"
 gem "rspec-rails", "~> 6.0"
+gem "concurrent-ruby", "< 1.3.5"
 
 gemspec path: "../"