Revert "Allow specifying the default table options for mysql adapters"

This reverts commit 8246b593bf.

There was concern about this modifying the behavior of past migrations.
We're going to add an way to modify the migration generator instead.

activerecord/CHANGELOG.md

@@ -1,8 +1,3 @@
-*   Allow specifying the default options for new tables on mysql and mysql2 in
-    database.yml, via the key `default_table_options`.
-
-    *Sean Griffin*
-
 *   Except keys of `build_record`'s argument from `create_scope` in `initialize_attributes`.
 
     Fixes #21893.

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -597,8 +597,7 @@ module ActiveRecord
       end
 
       def create_table(table_name, options = {}) #:nodoc:
-        default_table_options = @config.fetch(:default_table_options, "ENGINE=InnoDB")
-        super(table_name, options.reverse_merge(options: default_table_options))
+        super(table_name, options.reverse_merge(:options => "ENGINE=InnoDB"))
       end
 
       def bulk_change_table(table_name, operations) #:nodoc:

activerecord/test/cases/migration_test.rb

@@ -1020,23 +1020,4 @@ class CopyMigrationsTest < ActiveRecord::TestCase
     ActiveRecord::Base.logger = old
   end
 
-  if current_adapter?(:Mysql2Adapter)
-    def test_default_table_options
-      config = ActiveRecord::Base.configurations['arunit'].merge(
-        encoding: 'utf8mb4',
-        default_table_options: "ENGINE=InnoDB CHARACTER SET utf8mb4",
-      )
-      ActiveRecord::Base.establish_connection(config)
-
-      ActiveRecord::Base.connection.create_table(:foos) do |t|
-        t.string :emoji
-      end
-      ActiveRecord::Base.connection.execute("INSERT INTO foos (emoji) VALUES ('💩')")
-      emoji = ActiveRecord::Base.connection.execute("SELECT emoji FROM foos").first.first
-      assert_equal "💩", emoji
-    ensure
-      ActiveRecord::Base.connection.drop_table(:foos, if_exists: true)
-      ActiveRecord::Base.establish_connection(:arunit)
-    end
-  end
 end