Mysql, fix some AR test failing due mysql2_connection (database_exists? is implemented in abstract class)

  1) Error:
Mysql2AdapterTest#test_database_exists_returns_false_if_database_does_not_exist:
NoMethodError: undefined method `mysql2_connection' for ActiveRecord::Base:Class
Did you mean?  connection
    lib/active_record/dynamic_matchers.rb:22:in `method_missing'
    /home/jessec/bryk/vendor_gems/activerecord-jdbc-adapter/lib/arjdbc/mysql/adapter.rb:88:in `database_exists?'
    test/cases/adapters/mysql2/mysql2_adapter_test.rb:83:in `test_database_exists_returns_false_if_database_does_not_exist'

  ...

Author: JesseChavez

lib/arjdbc/mysql/adapter.rb

@@ -84,15 +84,6 @@ def initialize(...)
         @connection_parameters = conn_params
       end
 
-      def self.database_exists?(config)
-        conn = ActiveRecord::Base.mysql2_connection(config)
-        conn && conn.really_valid?
-      rescue ActiveRecord::NoDatabaseError
-        false
-      ensure
-        conn.disconnect! if conn
-      end
-
       def supports_json?
         !mariadb? && database_version >= '5.7.8'
       end