[Fix] GUDB name consistency

[danibene]

Description

This PR aims to improve consistency in the naming of the GUDB database for R-Peak annotations and raw ECG data. I think a difference in naming could be problematic when selecting subsets of data for benchmarking:

NeuroKit/neurokit2/benchmark/benchmark_ecg.py

Lines 83 to 85 in d42a230

	# Extract the right slice of data
	ecg_slice = ecgs[(ecgs["Participant"] == participant) & (ecgs["Database"] == database)]
	rpeaks_slice = rpeaks[(rpeaks["Participant"] == participant) & (rpeaks["Database"] == database)]

Proposed Changes

I changed download_gudb.py so that the database name for R-peaks uses an underscore instead of parentheses:

NeuroKit/data/gudb/download_gudb.py

Line 44 in d42a230

anno["Database"] = "GUDB (" + experiment + ")"

Such that it matches the corresponding name for raw ECG data:

NeuroKit/data/gudb/download_gudb.py

Line 38 in d42a230

data["Database"] = "GUDB_" + experiment

Checklist

• I have read the CONTRIBUTING file.
• My PR is targeted at the dev branch (and not towards the master branch).
• I ran the CODE CHECKS on the files I added or modified and fixed the errors.