List all bundled providers in the retrieval docstring

The module docstring named only the OpenAI, Cohere-rerank, and TEI
providers, omitting the Jina providers and the new CohereEmbeddingProvider.
List the full bundled set (OpenAI embed, TEI embed + rerank, Jina and
Cohere embed + rerank) to match what the module exports.

Author: chris-colinsky

src/openarmature/retrieval/__init__.py

@@ -1,9 +1,10 @@
 """The retrieval-provider capability.
 
 The embedding + rerank provider protocols, their response types, and the
-bundled reference providers (an OpenAI-compatible embedding provider, a
-Cohere-shape reranker, and the TEI embedding + rerank providers). Embedding and
-rerank are sibling surfaces on the same capability.
+bundled reference providers: an OpenAI-compatible embedding provider, the
+TEI embedding + rerank providers, and the Jina and Cohere embedding +
+rerank providers. Embedding and rerank are sibling surfaces on the same
+capability.
 """
 
 from __future__ import annotations