Polish RetryTask

[quaff]

1. Fix wrong type name in assertion message.
2. Rename retryTemplate to retryOperations to match type better.

[jhoeller]

Well spotted - however, while this is debatable, it is actually intentional. JdbcClient and JmsClient follow the same pattern of accepting Operations interfaces while suggesting the Template classes both in the parameter name and the assertion message. The rationale is that the common thing to pass in there is a template instance, with the operations interface primarily declared for testability. In other words, the operations interface is just a facade for a specific template rather than an independent contract.