[Test] Anthropic Passthrough: Bump Streaming Cost-Injection Test To Haiku 4.5

test_anthropic_messages_streaming_cost_injection hits the proxy's
/v1/messages route, which routes via the anthropic/* wildcard to
api.anthropic.com. The 404 surfaced in the test was Anthropic's own
not_found_error propagated back through the proxy (visible from the
x-litellm-model-id hash on the response — the proxy did route).

Same root cause as the prior commit: the legacy claude-4-sonnet-20250514
alias is no longer recognized by Anthropic's main API under the new key.
Swap to claude-haiku-4-5-20251001 — same routing path, canonical model.

tests/pass_through_tests/test_anthropic_passthrough.py

@@ -333,7 +333,7 @@ async def test_anthropic_messages_streaming_cost_injection():
     }
 
     payload = {
-        "model": "claude-4-sonnet-20250514",
+        "model": "claude-haiku-4-5-20251001",
         "max_tokens": 10,
         "stream": True,
         "messages": [{"role": "user", "content": "Say 'Hi'"}],