Remove tests for not swallowing exceptions.

From PR, @tenderlove would prefer to not maintain these tests.

activerecord/test/cases/adapters/mysql/connection_test.rb

@@ -164,27 +164,6 @@ def test_mysql_set_session_variable_to_default
     end
   end
 
-  def test_mysql_begin_db_transaction_can_throw_an_exception
-    @connection.expects(:exec_query).with('BEGIN').raises('OH NOES')
-    assert_raise RuntimeError do
-      @connection.begin_db_transaction
-    end
-  end
-
-  def test_mysql_commit_db_transaction_can_throw_an_exception
-    @connection.expects(:execute).with('COMMIT').raises('OH NOES')
-    assert_raise RuntimeError do
-      @connection.commit_db_transaction
-    end
-  end
-
-  def test_mysql_rollback_db_transaction_can_throw_an_exception
-    @connection.expects(:execute).with('ROLLBACK').raises('OH NOES')
-    assert_raise RuntimeError do
-      @connection.rollback_db_transaction
-    end
-  end
-
   private
 
   def run_without_connection

activerecord/test/cases/adapters/mysql2/connection_test.rb

@@ -89,27 +89,6 @@ def test_logs_name_rename_column_sql
     @connection.execute "DROP TABLE `bar_baz`"
   end
 
-  def test_mysql_begin_db_transaction_can_throw_an_exception
-    @connection.expects(:execute).with('BEGIN').raises('OH NOES')
-    assert_raise RuntimeError do
-      @connection.begin_db_transaction
-    end
-  end
-
-  def test_mysql_commit_db_transaction_can_throw_an_exception
-    @connection.expects(:execute).with('COMMIT').raises('OH NOES')
-    assert_raise RuntimeError do
-      @connection.commit_db_transaction
-    end
-  end
-
-  def test_mysql_rollback_db_transaction_can_throw_an_exception
-    @connection.expects(:execute).with('ROLLBACK').raises('OH NOES')
-    assert_raise RuntimeError do
-      @connection.rollback_db_transaction
-    end
-  end
-
   private
 
   def run_without_connection