Updated readthedocs yaml

[AlArgente]

Update readthedocs.yaml to works with the ReadTheDocs web page.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
flex/common
utils.py	75	15	80%	135–151, 189
flex/data
dataset.py	154	29	81%	53–59, 130, 200, 202, 214, 222–238, 288–289, 306–307, 314, 322, 327, 334–335, 397, 413–414
fed_data_distribution.py	182	1	99%	397
lazy_indexable.py	79	2	97%	55, 89
pluggable_datasets.py	62	1	98%	27
flex/datasets
federated_datasets.py	45	26	42%	35, 39–71, 75–89, 102
flexible_datasets.py	11	3	73%	29, 46–47
flex/pool
aggregators.py	50	4	92%	55–56, 145–146
primitives_pt.py	63	50	21%	46, 61–63, 104–122, 158–170, 197–206, 235–244
primitives_tf.py	42	7	83%	74–84
TOTAL	1270	138	89%

Tests	Skipped	Failures	Errors	Time
188	4 💤	0 ❌	0 🔥	1m 36s ⏱️