Revert "A safe way to create class variables in a multisite environment."

The approach taken by this interface was flawed. We need a better
solution.

spec/multisite/multisite_class_var_spec.rb

@@ -1,67 +0,0 @@
-require 'rails_helper'
-require 'multisite_class_var'
-
-RSpec.describe MultisiteClassVar do
-
-  it "will add the class variables" do
-    class_with_set = Class.new do
-      include MultisiteClassVar
-      multisite_class_var(:class_set) { Set.new }
-      multisite_class_var(:class_array) { Array.new }
-    end
-
-    class_with_set.class_set << 'a'
-    class_with_set.class_array << 'c'
-
-    expect(class_with_set.class_set).to contain_exactly('a')
-    expect(class_with_set.class_array).to contain_exactly('c')
-  end
-
-  context "multisite environment" do
-    let(:conn) { RailsMultisite::ConnectionManagement }
-
-    before do
-      @original_provider = SiteSetting.provider
-      SiteSetting.provider = SiteSettings::DbProvider.new(SiteSetting)
-      conn.config_filename = "spec/fixtures/multisite/two_dbs.yml"
-      conn.load_settings!
-      conn.remove_class_variable(:@@current_db)
-    end
-
-    after do
-      conn.clear_settings!
-      [:@@db_spec_cache, :@@host_spec_cache, :@@default_spec].each do |class_variable|
-        conn.remove_class_variable(class_variable)
-      end
-      conn.set_current_db
-      SiteSetting.provider = @original_provider
-    end
-
-    it "keeps the variable specific to the current site" do
-      class_with_set = Class.new do
-        include MultisiteClassVar
-        multisite_class_var(:class_set) { Set.new }
-      end
-
-      conn.with_connection('default') do
-        expect(class_with_set.class_set).to be_blank
-        class_with_set.class_set << 'item0'
-      end
-
-      conn.with_connection('second') do
-        expect(class_with_set.class_set).to be_blank
-        class_with_set.class_set << 'item1'
-      end
-
-      conn.with_connection('default') do
-        expect(class_with_set.class_set).to contain_exactly('item0')
-      end
-
-      conn.with_connection('second') do
-        expect(class_with_set.class_set).to contain_exactly('item1')
-      end
-
-    end
-  end
-
-end