Increase starting threshold to 0.5 quantile

[laurencejackson]

Resolves #322 by increasing Li threshold starting value to 0.5 quantile.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
hazenlib
HazenTask.py	25	4	84%	18, 32–34
__init__.py	147	38	74%	138, 142, 152, 157, 194, 201–206, 217, 220–227, 247–249, 267–269, 288–290, 299, 304, 310, 361, 384–386, 394–395, 399
exceptions.py	21	4	81%	17–21
relaxometry.py	317	90	72%	238–256, 631, 690–692, 746, 794–816, 834–849, 1174–1177, 1186–1189, 1201–1214, 1217–1222, 1233–1263
shapes.py	20	9	55%	13, 16, 24–29, 32
snr_map.py	111	5	95%	408, 413–415, 444
tools.py	84	8	90%	43–50, 92, 101, 117
hazenlib/tasks
acr_ghosting.py	116	42	64%	33–53, 91–93, 123–125, 161–194
acr_uniformity.py	89	32	64%	34–54, 121–138
ghosting.py	150	51	66%	18–32, 47, 109–110, 114, 124–125, 151–153, 170–172, 218–256
relaxometry.py	7	2	71%	10–11
slice_position.py	118	22	81%	31, 40–41, 103–104, 130, 210, 217–234
slice_width.py	356	52	85%	34–37, 107, 166–186, 451, 456–457, 463, 468, 530–531, 780–821
snr.py	163	66	60%	62–67, 161–179, 194–203, 221–231, 258–268, 273–283, 314–327, 332–340, 369–382
snr_map.py	7	7	0%	1–11
spatial_resolution.py	246	44	82%	36–39, 62, 147, 206, 332–368
uniformity.py	78	19	76%	42–45, 91–92, 99, 133–147
TOTAL	2071	495	76%

Tests	Skipped	Failures	Errors	Time
180	0 💤	0 ❌	0 🔥	2m 22s ⏱️

[tomaroberts]

LGTM