(debug) openbis: ab_prefix argument of upload_data should not be Path, but a str

[Ohyeon5]

Fix the problems when --ab_prefix "" the files are not properly uploaded.

• It was because the --ab_prefix "" type was set to Path; thus, it made arbs.ab_prefix to be . rather than an empty str.
• Type of the ab_prefix was set back to str

Also, minor typos are fixed