Do not provide a default for KnowledgeSource Value

Sources/SpeziFoundation/SharedRepository/KnowledgeSource/KnowledgeSource.swift

@@ -13,7 +13,7 @@
 /// is set to `Self`.
 public protocol KnowledgeSource<Anchor> {
  /// The type of a value this `KnowledgeSource` represents.
- associatedtype Value = Self
+ associatedtype Value
  /// The ``RepositoryAnchor`` to which this `KnowledgeSource` is anchored to.
  associatedtype Anchor: RepositoryAnchor
 }