docs: Fix DelegatedRole rendering

Improve class DelegatedRole docstring in order to be rendered
correctly in the documentation built with sphinx and autodoc.

Signed-off-by: Teodora Sechkova <tsechkova@vmware.com>

tuf/api/metadata.py

@@ -984,11 +984,12 @@ class DelegatedRole(Role):
     """A container with information about a delegated role.
 
     A delegation can happen in two ways:
+
         - paths is set: delegates targets matching any path pattern in paths
         - path_hash_prefixes is set: delegates targets whose target path hash
-            starts with any of the prefixes in path_hash_prefixes
+          starts with any of the prefixes in path_hash_prefixes
 
-    paths and path_hash_prefixes are mutually exclusive: both cannot be set,
+        paths and path_hash_prefixes are mutually exclusive: both cannot be set,
         at least one of them must be set.
 
     Attributes: