Add task to cleanup subject keywords

[alinvetian]

Closes: datadryad/dryad-product-roadmap#4837

[ahamelers]

Seems to work, though I'd also like @ryscher to test!

[ryscher]

When the first SQL statement runs, it replaces offending characters with empty values. This leaves the dataset having a Subject object that has no subject field, and the subjects for the dataset will not render.

[alinvetian]

@ryscher I entirely removed the first query since it was removing the subject value for 412 subjects that was not supposed to.

Also there are multiple subjects like [ 54 ] Cohort studies that became Cohort studies while having only 2 digits