Adjust get-sequence's space limit

[misialq]

As a plugin user, I want the space limit within get-sequences to be adjusted so that I can use as much of my free space as possible when downloading sequences.

Subtasks:

• [ ] Gather a list of run/project IDs to run the tests with
• [ ] Perform and document space requirement tests
• [ ] Adjust the space limit in the code

Note: Initial adjustment worked pretty good - after #80 there's some space being freed up at every fetch iteration so we need to re-adjust.