Convert docstrings from rst to markdown syntax

[wm-wm-wm]

Change Summary

All docstrings converted from rst to markdown syntax

Related issue number

[DOP-37517]

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[github-actions]

Coverage Report •

File	Stmts	Miss	Branch	BrPart	Cover	Missing
horizon/backend/dependencies
stub.py	16	3	6	2	81%	34, 39, 43
horizon/backend/settings/auth
__init__.py	10	2	0	0	80%	8–9
ldap.py	43	6	4	3	86%	24, 27–28, 147–149
horizon/backend/settings/server
cors.py	19	3	4	3	84%	63–65
static_files.py	14	4	4	2	71%	32–33, 35–36
horizon/client
base.py	96	12	28	6	87%	18, 67, 74, 104, 108, 147–149, 151, 153, 162, 164
sync.py	99	1	6	1	98%	1090
horizon/client/auth
access_token.py	34	1	4	1	97%	41
horizon/commons/exceptions
auth.py	12	2	0	0	83%	29, 33
bad_request.py	13	2	0	0	84%	33, 37
entity.py	39	1	2	1	97%	42
permission.py	17	2	0	0	88%	37, 41
service.py	10	2	0	0	80%	27, 31
TOTAL	2528	202	308	83	92%