ref: simplify close_streaming_response using .getvalue() (#71160)

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src/sentry/testutils/helpers/response.py

@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from collections.abc import Iterable
-
 from django.http.response import HttpResponseBase, StreamingHttpResponse
 
 
@@ -12,5 +10,4 @@ def close_streaming_response(response: HttpResponseBase) -> bytes:
     avoiding a `ResourceWarning`.
     """
     assert isinstance(response, StreamingHttpResponse)
-    assert isinstance(response.streaming_content, Iterable)
-    return b"".join(response.streaming_content)
+    return response.getvalue()