remove unused .default_strategy ORM adapter method.

ADAPTERS.md

@@ -50,7 +50,7 @@ The file structure you end up with will look something like this
 #### orm_name.rb
 
 File `orm_name.rb` **must** do the following:
-  * define module methods `.default_strategy` and `.available_strategies` on DatabaseCleaner::OrmName.
+  * define module method `.available_strategies` on DatabaseCleaner::OrmName.
   * require all the gems strategies
   * configure DatabaseCleaner with the default strategy for the ORM.
 
@@ -70,10 +70,6 @@ module DatabaseCleaner
     def self.available_strategies
       %i[transaction truncation deletion]
     end
-
-    def self.default_strategy
-      :transaction
-    end
   end
 end
 

lib/database_cleaner/spec/shared_examples.rb

@@ -8,11 +8,6 @@ end
 
 RSpec.shared_examples_for "a database_cleaner adapter" do
   it { expect(described_class).to respond_to(:available_strategies) }
-  it { expect(described_class).to respond_to(:default_strategy) }
-
-  it 'default_strategy should be part of available_strategies' do
-    expect(described_class.available_strategies).to include(described_class.default_strategy)
-  end
 
   describe 'all strategies should adhere to a database_cleaner strategy interface' do
     described_class.available_strategies.each do |strategy|