Remove pulsar/util/pastescript?

Seems to be a copy of galaxy's `lib/galaxy/util/pastescript`

Noticed here: https://github.com/galaxyproject/galaxy/pull/12755 .. if not removed the change would imply a little change in pulsar's pastescript module, i.e. replace `galaxy.util.getfullargspec` by `inspect.getfullargspec`.

Start by locating pulsar/util/pastescript and checking whether the module is still referenced elsewhere in Pulsar. Read the related Galaxy pull request for context, then verify that removing the duplicate module leaves no broken references or required behavior behind.

Written by the indexing model from the issue text.