Bug in HydroPSO package

As reported in #52 (comment 19046), there was a bug in the last version of hydroPSO package used in vignette V02.1_param_optim. The corresponding chunk is currently skipped for the tests.

The maintainer has commmited an update to CRAN (#52 (comment 19346)). The chunk using hydroPSO can now be integrated into the tests.